Since the earth is trapped in orbit around the sun by the sun's gravity, how can a wave moving out from an object in turn pull a second object back towards the object that generated the wave? In other words, how can gravity waves moving out from the sun at the same time pull the earth towards the sun? The answer to your first question is in a recent answer. In your second answer, you are confusing gravity with gravitational waves.
Our picture of gravity is that mass like the sun deforms the space around as in the animation above. Something like the earth orbiting the sun is not really feeling a force, it is following the contour of the space. Do not take this simplistic model too seriously, it is really the four-dimensional space-time which is "deformed". But, if something accelerates, like the earth going around in its orbit, it will send out ripples and those are the gravitational waves.
On the scale of this animation, the waves the orbiting earth is sending out are far too tiny to be seen. But, if the objects orbiting are much more massive, like the two orbiting black holes which were observed in the recently reported observation of the waves, the waves are much bigger. Ok so you know how they say, "if you look up at the stars in the night sky, you are seeing light that's taken millions of years to travel to earth, so you are seeing Into the past potentially"?
Ok so here's the question. If say I'm on a planet in the Andromeda galaxy, and you're on earth looking at me with a super telescope to where u can actually see me wave at you and let's say we agreed on a specific time and date to do this. If I start waving at you at the exact time you are observing me with the telescope, do you ever see me wave or does it take millions of years to see me wave at you? How do you plan to agree on a specific time and date to wave if it takes millions of years to communicate.
Just imagine that there is a star exactly halfway between you and me and we have, by some magic, both been instructed to do our things wave and look when we observed the star to become a supernova. If you and I are separated by a million light years, I will not see you wave until a million light years have passed. Furthermore, the supernova would have occurred a half million years before either of us saw it.
Why is it that when I listen to music on my PC through an external speaker set and my cell phone right next to me gets messages, etc Your cell phone is both a receiver and a transmitter of radio waves. The transmitted radio waves may be detected by your sound system. When a television set is turned on it often generates an electrostatic field.
You can still feel this charge if you move your arm near the screen shortly after the set has been turned off. Why does this field not disappear as soon as the television set has been turned off? You probably have an old cathode ray tv. The screen is coated with a phosphor which glows if you strike it with an electron. Electrons are shot from the rear of the tube to cause a picture to be formed.
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Some of these electrons are still on the screen when you turn off the power. Ships are often built on ways that slope down to a nearby body of water. Is this done because the added weight would cause the ship to slide down the ways prematurely? Friction can be a tricky business, but the simplest behavior is that the frictional force increases proportional to the weight. But the force of the gravity trying to slide the weight down the slope is also proportional to the weight.
Therefore, doubling the weight of the ship should not increase its tendency to slide down. Besides, if this were a concern you could always temporarily block the path down the slope like placing blocks in front of a vehicle on a slope to keep it from rolling. I suspect the real reason is that the structure of the ramp is probably not strong enough to support the full weight of the ship. If one wanted to turn a cylinder 5 feet in outer diameter and 3 feet inner diameter and the reel is supported via a 2 in bar through the center of it Look like this i suppose more like a reel A rope is wound around the outer diameter and pulled think of a yo yo how much torque would you have to put on the rope to get it to turn?
Can you show how one can figure that? It would depend on how long you pulled, what the mass of the hollow cylinder is, and how much friction there is. I have asked several people to give an answer on this and no one has been able to answer it for me. So I attached a pic I just drew out for you On the pic you see that the master reel is lbs I want to pull the rope off the reel and put on another reel I would like to do so at 35 rpm on the small reel The small reel is just like the large reel but the OD is 24 inches and the center of the reel is 12 inches First you have a misconception.
If friction is truly negligible, any torque, no matter how small, will start the big reel turning. It is a matter how long you want to wait until you get up to 35 rpm on the smaller reel. For several reasons this is a quite complicated engineering problem. The most important problem to deal with, I think, is that as rope comes off the larger reel its weight gets smaller and its radius gets smaller; at the same time the smaller reel gets larger and heavier.
So if you want to keep the smaller reel going at a constant 35 rpm the larger reel will have to change its speed if the rope is to remain taught. So, I will only address the question of how you start up just to demonstrate how torque determines what happens. Since it is the smaller reel you want to go 35 rpm, the upper reel would need to have an angular velocity of 0. Assuming that your idea is to use the empty reel to pull the heavier reel via the rope. Again, I will neglect the torque necessary to get the smaller reel going since it will presumably be lighter than the already neglected weight of the heavier reel.
In your case, the angular acceleration would be the final angular speed divided by the time to get there; so if you want to get up to speed in 10 seconds, the angular acceleration would be 5. You see, now, why there is no answer to your question: A longer spin-up time would need a smaller torque. I've got a basic question about signal processing within the discipline of management information systems.
Today, some basic signals within management information systems, which people come across are electrical, light fiber optics , and radio waves. Is it true that radio waves are a type of electromagnetic radiation or many types of electromagnetic waves, which can travel at the speed of light? I didn't think it was possible for anything to travel at the speed of light. As I understand it, the speed of light in a vacuum, such as space or other, commonly denoted c, is a universal physical constant that's very important in many areas of physics. The speed of light, it travels approximately 3. Can anything you know of travel at the speed of light especially radio waves?
When a physicist refers to "the speed of light" she is talking about the speed of electromagnetic radiation in a vacuum. Of all the possible wavelengths of light, visible light is but a tiny fraction. Whether light is a particle or wave? Which is right and why? Light is not a particle or a wave, it is a particle and a wave. This is called wave-particle duality. If you design an experiment to observe a particle, you will observe a particle; and, if you design an experiment to observe a wave, you will observe a wave.
If you have a wind up toy car, meaning that when it starts you can wind it up to maximum and have a constant force pushing it forwards, how would you expect the distance in travels to change as you add mass to it? The spring will deliver a certain amount of energy. Giving the same amount of energy to a large mass and a small mass will result in the small mass going faster.
The small mass will therefore go farther. This assumes that the wheels never slip. If all things with mass have a proportional amount of gravity and gravitational waves were recently observed to have been produced by 2 black holes converging, is it correct to deduce that all things with mass produce gravitational waves proportional to their mass? Any object with mass which accelerates should radiate gravitational waves. Wave to someone and you cause gravitational waves. However, gravity is the weakest force in nature so, for the the waves to have a big enough amplitude to be detectable, the masses must be extremely large as in black holes.
How fast do gravitational waves move? Is that rate constant? The speed of gravitational waves has never been measured. The speed at which a gravitational field propogates should be the same but it has never been measured either; this would determine, for example, if the sun suddenly disappeared how long it would be until the earth stopped orbiting. The theory of general relativity, which predicts gravitational waves, say that the speed of gravity should be the same as the speed of light.
The recent observation of gravitational waves determined the distance to the source to be about 1. Whatever the speed, there is no reason to think that it would not be constant everywhere in empty space. A car is moving forward through a road. Which part of the wheel of the car moves fast- the upper part or the lower part of the wheel? Inasmuch as the part of the tire in contact with the road is at rest, the answer should be obvious. You should be able to show that the top of the wheel is moving forward with twice the speed of the car.
Has anybody ever done the double slit experiment on a very large scale. By large I mean physically where the electrons are shot at tow slits several feet wide separated by an even greater distance from a large distance away to see if the electrons themselves will still manage to make it through the slits at all? As long as the electrons are unobserved acting as a wave they should still continue to go throught the slits and produce a wave pattern behind the slits regardless of scale. However does this deteriorate at some point and break down to cause the electron to again act as a particle and simply hit the mass between the two slits and if so could this be somehow used as a physical means to measure the energy of the electron?
Could an electron with a greater energy then once again act as a wave? As far as I know, nobody has ever done a true double-slit experiment with electrons at all. Given the extraordinarily short wavelength of an electron, the spacing between slits would have to be on the order of 10 m and you just cannot make physical slits that close because that is like the distance between atoms.
What is actually done is to shoot electrons at a single crystal and you get a double-slit like experiment. For diffraction to be observable the slit spacing and slit width must be small compared to the wavelength of the wave. I am doing an experiment on factors affecting the travel distance of a toy car from down a ramp and thought it would be a good idea to understand how a physicist thinks of things.
My question is, how do you think weight of an object affects the distance it will travel after going down a ramp? The best discussion I have seen of the physics of pinewood derby races is this youtube video. You will see that what matters more than the added weight is where you put it. Thanks to my son Andy for pointing me to this video; his son and my grandson Finn placed second in the Cub Scout pinewood derby last year on the strength of the tips here! Hello, question in physics. Why would the speed of a rollercoaster with potential energy of 5MJ have less than that predicted for a perfect frictioless track at the bottom of the slope?
A roller coaster has wheels and some of the kinetic energy would be in their rotation, not in the speed of the cars. Of course, if the track were perfectly frictionless the wheels would not go around at all. Maybe your problem means no energy lost to friction? Or maybe the bottom of the slope is not at the zero of potential energy? What will happen if we fill water in the tyres of our cars instead of air? Does it have any effect?. Three important issues I can think of. First, it would add a lot of weight to the vehicle which would hurt your gas economy. Second, the moment of inertial of a wheel would be larger requiring a larger torque having to be exerted for either acceleration or braking.
Third, air is compressible and water is not and so the wheel would not have a cushioning effect on the ride. We say that time slows as we accelerate. Is time some existent entity that can slow? Or is it the accelerated object [or particles it is composed of] that somehow "ages" more slowly because of the energy applied to it? You do not need to talk about acceleration. Time dilation says that clocks which have a high velocity relative to you run more slowly than your clocks.
And, it is not that they look like they are running slower, in fact they may look to be running faster, but they actually do run slower; see faq page for links discussing this. The best way to see this, I think, is to consider the light clock discussed in an earlier answer. To understand the light clock, you must accept that the speed of light is the same for all observers; see the faq page. Also, to help you with understanding time dilation, read about the twin paradox. What would happen if you threw a baseball at the speed of sound? At such a large speed, air drag has an enormous effect on ball.
To see the mathematical details see earlier answers for a lacross ball and a baseball. I will make the same assumption that I did in those answers that the amount by which the ball will fall will be very small compared to its horizontal distance and the speed acquired in the vertical direction will be very small compared to its horizontal speed. So I will ignore the small effect which the vertical motion will have on the horizontal motion. During the same time, the ball will fall approximately 5 m and so, if launched horizontally from a height of 5 m will hit the ground in one second as shown below.
Be sure to note the difference in vertical scales; an insert shows the trajectory drawn to scale. The small distance fallen is the justification for my approximations above. I am new to Quantum Mechanics and I am a little confuse about the representation of the spin. But if I have multiple options for the spin e. I do not know what you mean about the " … cos 2 of half of the angle…", but you seem to not know what, e. Does a uniformly charged ring rotating at constant angular velocity about its axis perpendicular to its plane radiate electromagnetic waves? Because the magnetic field produced is constant hence there is no changing magnetic field and hence no em waves.
Any accelerated charge radiates. The radiation from a charge moving in a circle is called synchrotron radiation. The theory of synchrotron radiation is very difficult and not appropriate to do here. I can tell you, though, that the energy which the charges have is so low that the power radiated would be immeasurably small. I just saw a music video in which a group of performers appear to be in an aeroplane cabin in free-fall for 2 minutes and 40 seconds. The choreography is spectacular, and it appears to have been done in ONE take!
How far would the plane have had to descend to maintain zero gravity conditions for seconds? This video was shot in Russia in a reduced-gravity jet provided by S7 Airlines. Weightlessness is not achieved by falling but by following the parabolic path which a projectile would follow. Imagine that someone shot you from a cannon with a speed of mph the typical speed of a commercial jet. If there were no air drag, you would follow a parabolic path. The plane which contains you now follows that exact path and that is how you appear to be weightless. An alternative way would be for the plane to simply go straight down with an acceleration of 9.
Anyhow, back to your question, I could not find reference to any such parabolic flight lasting longer than 30 s, so the video must have been shot in more than one take. Because this is such an unfamiliar environment, I cannot believe that, even with a lot of practice, it could be done in a single take without errors. And, if the plane were simply falling for s, it would have to have started at an altitude of about 80 mi far higher than a plane can actually fly and would end with a speed of about mph far faster than the plane could fly without disintegrating.
Is this exciting for you?? I dont really understand it but I'm trying to Observing gravitational waves has been a holy grail of physics since before I was an undergraduate like 55 years ago, gasp! So yes, it is pretty exciting news. This is actually just the first direct evidence for gravitational waves. Indirect evidence was found when observing a pair of stars orbiting each other and spiraling in toward a collision. The loss of energy turned out to be exactly equal to the amount of energy they would lose if radiating gravitational waves.
A nobel prize in physics was awarded in for this observation. The animation below shows the predicted gravitational waves from two neutron stars orbiting each other. A bit off beat from what you are usually asked. Jews are not allowed to drive a car on the Sabbath. The problem is the internal combustion engine which creates a spark in the piston igniting the gasoline. In a Tesla automobile does the magnetic field around the motor ultimately create a spark driving the wheels?
It is natural, if you have a little knowledge about electric motors, to think of the magnetic field driving the motor. In fact, a magnetic field never does work because of its very nature. Although the presence of magnetic fields is imperative, work is always done by electric fields they produce. Most electric motors have "brushes", contacts which slide on the rotating armature, and small sparks are inevitable when electrical contact is made or broken. The Tesla electric car, however, employs a type of motor called an induction motor which is brushless and is therefore probably sparkless.
Hi this may be a hard question but If I wanted to run gpm through a foot run with 50 feet of fall what size pvc pipe would this take? This is all gravity. At first I just did a calculation with no corrections for viscosity or drag. But then I worried about the fact that a pipe that long is likely to have significant drag over its length.
It is a pretty complicated engineering calculation and I was unfamiliar with many of the parameters. But I did find a web site which seems to have made it easy for me by including a calculator. Frankly, I have no idea what the roughness coefficient is, but it suggests a value of for plastic. The result is below. As you can see, to get a flow rate of about gpm would require a pipe with diameter of about 10 in. What if Einstein's General relativity wrong? Would all physics need to be rewritten? Actually, the theory of general relativity, essentially the theory of gravity, has very little effect on most of physics.
Furthermore, like all theories, it is an idealization and approximation and is already "wrong" at some level. It is also incomplete because there is no theory of quantum gravity and it does not address the issues of dark matter and dark energy. If I place a liquid filled container on a scale and suspend a mass with greater density than the liquid within the liquid and then release the mass, will the scale register the full weight of the mass while the mass is in motion falling as compared to when the mass has settled on the bottom?
Will the scale read the same while the mass is accelerating as when it has achieved terminal velocity? Your second question indicates that you understand the answer will be different depending on whether the falling mass is accelerating or not. The figure shows that the weights of the fluid and the container will act down on the scale. Now look at the falling object. In addition to its weight there are two upward forces, the buoyant force B and the drag force D ; these are both forces which the fluid exerts on the object.
But Newton's third law says if the fluid exerts a force on the object, the object exerts an equal and opposite force on the fluid. There is an earlier q uestion similar to yours except the object is rising instead of sinking. Have scientists done experiment on what is the value of gravity below the earth surface as depth increases? The deepest hole ever drilled is only about 12 km deep. I could not find any reference to attempts to measure g at various depths down this hole. Since the radius is about 6. There are models of the density of the earth, though, which have been determined by observing waves transmitted through the earth during earthquakes or nuclear bomb tests; these are believed to be a pretty good representation of the radial density and can be used to calculate g.
The two figures above show the deduced density distribution and the calculated g. Usually in introductory physics classes we talk about the earth as having constant density, but as you can see, that is far from true—the core is much more dense than the mantles and crust. If it were true, g would decrease linearly to zero inside the earth. However, if you have detailed information on density distribution, there is really no need to measure g. I'm so confused, my question is that if i hit the chair and chair change it's position from it's original position, then where is the reaction of chair and how according to third law of motion ANSWER: The force which you exert is on the chair.
The reaction force is the force which the chair exerts on you. Only forces on the chair determine how the chair will move. I have a question thats driving me nuts. Say on a circle that spins, there are two points, one on the outer rim and one close to the rim. Both are in line with each other and are traveling at the same time but the distance of the point on the outside making one revolution is longer than the distance of the one on the inside.
So the speed are the same but the distance of the inner point is shorter. The time they take to complete one rotation is also the same as the two points stay in line with each other. So speed is equal to distance divided by time as far as i know. Something have to give, don't understand it. The two points have the same angular speed but different translational speeds. For example, if the distance from the center is 1 m to the rim and 0. Scientists say that centrifugal force is the only thing stronger than the pull of a black hole. What i want to know is what would happen if somehow the material around a black hole stopped spinning around it what would happen and how might the spinning be stopped?
Funny, I never heard scientists say this. All that I can imagine you are thinking about is that in the right circumstances an object might orbit around a black hole just like the earth orbits around the sun without falling in. But, the black hole exerts such a large force that even light can orbit at a certain radius which is outside the Schwartzchild radius; inside the orbiting light, nothing with mass could have a stable orbit. Obviously, if you stopped this orbiting, anything would fall into the black hole. Recent feedback from Heathrow airport suggests some of the passengers bags are sticking to the conveyer belts and are being miss-directed.
I have advised our supplier of this, they have sent through the data spec sheet but there is no mention of COF, on speaking with them they have never had this question raised before. Personally, I do not think this Is an issue with our film but more where customers themselves are wrapping their own bags with home use film.
However, I need to provide proof that the film we are using does not have any adhesive properties. My question is — would the COF affect this and how do I get the actual information on the film? The force of friction f depends on only two things: There are two kinds of COFs, kinetic and static. Once you have that, use it as an incline on which to place a wrapped suitcase.
Slowly increase the slope of the incline until the suitcase just begins to slide. I have a hill approximately 25 degree slope and feet in length. The anticipated speed is approximately 4 feet per second and at most I will have only two people on the tow rope at one time.
TODAY, 12 July 2007
I can only give you a rough answer. I will calculate the power needed to lift two large people total mass kg up the hill. I will work in SI units because that is the system in which the watt is the unit of power. I guess I would throw in a safety factor to account for friction and other energy losses, so maybe a 2 kW motor would do you.
The voltage and gear box are not really relevant in determining the power. I am not an engineer, so you should get a second opinion! A lb 8'x8' box that is 3'6" tall is lifted at one of the four side so that the opposite side acts as a pivot on the ground like a strong man flipping a giant tire in a a world strongest man competition.
How much actual weight is being lifted? Well, that depends on how you lift it. Let's assume that you lift it so that you cause it to rotate with uniform speed. One way that you could accomplish this is to push in a direction perpendicular a line drawn from where you are pushing and the edge on the box remaining on the floor. Of course there are lots of other ways you could lift it which would be more efficient if your aim was to tip it over; for example, you could start pushing horizontally once you got it off the ground so that the floor would hold up all the weight rather than half the weight.
There is an old answer very similar to yours that you might be interested in. I f a tennis ball and a football is thrown from a certain hieght then which ball will land first? I will assume that you do not mean an American football, rather a soccer ball. Also, it is not unambiguous what " …thrown from a certain height…" means.
Imagine that we just drop each from some height. If air friction is ignored, they hit the ground simultaneously; this would approximately be the case if they were dropped from a few meters. However, air drag becomes more important as the speed increases. The tennis ball will easily win the race because it continues accelerating long after the soccer ball stopped accelerating.
I love hearing about new discoveries from particle accelerators, but one aspect of them confuses me. Why don't these particles approach infinite mass and compress time from our perspective? Stable particles, those usually accelerated, do not carry clocks with them; but, if they did, those clocks would run slowly compared to yours. Some particles do carry clocks, those which are unstable. Suppose that the average lifetime of some particle were 1 s and its speed was 0.
The accelerated particles do indeed approach infinite mass but they have a really long way to go to get there even in the most powerful accelerators; see an earlier answer. It is not of any commercial interest to me, but the answer to my question has eluded me for a long time despite research and attempts to calculate it! If you could at least explain to me the correct method of attempting to work our the answer I would greatly appreciate it. Question background - horizontal restraint line.
It is 2m horizontally above ground level AGL. It is pre-tensioned to 50kg. A 20kg mass is suspended vertical above the horizontal rope and attached to the rope by a leash of 0. The 20 kg object is then dropped. At the time of peak impact force, the sag in the horizontal tension line is 1. Despite my best efforts I do not seem to be able to calculate theoretical i peak impact forces on the anchors ii peak impact force on the object.
I do however have peak impact force load cells that have recorded average i peak impact forces on the anchor kg and ii peak impact force on the object kg. It would be helpful if you could tell me the sag and forces when the mass is hanging at rest on its leash. I take it that the kg measurement is the tension in the leash. Let me first try to understand the data for the "loads" essentially the tension in the rope, T , and the tension in the leash, F in terms of simple physics; then I will try to generalize it.
Normally, physicists do not like to use kg to measure force, but I will go ahead and do that here. At this point what a physicist normally does is to try to understand the situation in terms of a simple spring model. If the rope is like a simple spring, i. The previous try indicates that the rope is probably not approximated as an ideal spring.
- Un verger dans le ventre (French Edition).
- Maudit tonneau: Comédie policière en deux actes (MON PETIT EDITE) (French Edition).
- More Sensible Thinking.
- .
My last attempt is to try to treat the rope more explicitly as an ideal spring, not using small approximations used above. I conclude that the rope is poorly approximated as an ideal spring and that to do any more detailed analysis of this problem would require measuring s as a function of the load by varying the load for the equilibrium situations. If possible, without the aid of the load cell values which I get by practically performing the drop test.
I understand how to calculate forces etc for the system at rest, but it is the dynamic falling system, deceleration etc that I am unable to clarify. You apparently did not understand my answer, particularly the second and third paragraphs. The first paragraph shows that the data are consistent with the simple model for the tensions in the ropes. I found these very encouraging. From the data for the dynamic point you could, of course, calculate the acceleration of the weight at that point.
Then I tried to model the rope as a simple spring, the tension is proportional to the stretch. I failed to do so in both attempts. You do not know the force which this rope will exert given a certain amount of stretch. Physics may be powerful, but you cannot do any predictive calculation if you are ignorant of the force. I have two data points but that is not enough if the force is not linear. The last paragraph suggests the only hope for having a predictive analysis: To do this you need to use many weights, say at 2 kg steps, and measure load 1 and sag.
This would give me the information necessary to do predictive calculations. Life in the real world is not always simple and analytical. It occurs to me you do not really need to hang varying weights because you have the load 2 device; just pull down on it until it reads 2 kg, 4 kg, 6 kg, etc. It is, of course, simple to calculate the speed the weight has just before the leash goes taught: A conductor, even though it is carrying a current, has zero net charge.
Magnetic fields exert forces on moving charges. In the conductor, negative charges are moving but positive charges are not. A magnetic field exerts no force on charges at rest. Do all five balls on a Newton's Cradle have to weigh the exact same amount in order for it work correctly? The balls on the ends need to be the same mass. However, you could no longer do the demonstration where if you send 2, 3, or 4 balls in that there would be 2, 3, or 4 balls out. If so, how are we able to separate 2 oppositely charges objects which are stuck together with our bare hands?
As often happens, you are applying an equation Coulomb's law without asking whether it applies. This law is true for two point charges or for two spherically-symmetric charge distributions; in the second case, R is the distance between the centers of the spheres. From what I understand, the inertia for a sphere is: Why is the radius included? Why is the volume of the sphere related to the resistance to change motion?
As long as any 2 objects have the same mass, why should they have different inertias? Inertia means the inherant ability of something to resist being accelerated. If you double the mass on which a given force acts, you halve the acceleration; mass is sometimes called inertial mass for this reason. For rotational acceleration, the rotational inertia depends not just on how much mass there is, it also depends on how it is distributed; for example, it requires much more effort to get a wheel with radius 1 m spinning than it does to spin a wheel with the same mass but a much smaller radius.
Miscellaneous
In rotational physics torque plays the role of force and moment of inertia plays the role of mass. If friction acts perpendicular to the direction of motion, if i place an object against a wall and let go, since the object is falling downwards, will friction from the wall cause the object to move away from the wall?
Also if I am standing still, gravity results in a downwards force so friction should act leftwards or rightwards. Which one is the correct one assuming that i am not moving? Friction does not act perpendicular to the direction of the motion but opposite it. When the surface is vertical there is no frictional force. This ignores irregularities in the wall and air drag.
If you are standing on a horizontal surface and not moving, the frictional force on you from the floor is zero. I am an engineer working on the reconstruction of a traffic accident where it is alleged that a car traveling over a railroad crossing became airborne at a speed lower than the posted speed of the road. The information that I have available includes the type and make of the car and the geometry of the road. Nothing in the engineering literature that I can find addresses this issue. Despite the five quarters of physics that I took long ago, I am having trouble finding the information that I need to model this.
This is sort of a classic introductory physics problem. I will do an approximation that the shape is a circle and that the car is a point mass. You can then generalize to your case from there or else give me more information. Note that it is independent of the mass. One thing which occurs to me though is, since you know the car and railroad crossing, why don't you just do the experiment and drive it over the crossing? When i place an object in between my 2 palms, why does it not fall?
My palms only supply horizontal force, where does the vertical force come from to hold the object between my palms without falling? You are wrong to say that your " …palms only supply a horizontal force…" When surfaces are in contact, the forces they exert on each other have components both perpendicular normal and parallel friction to the surfaces. It is the friction which holds the object. If the object were very heavy, say lb, and your hands were greased, you would not be able to hold it up because the frictional forces would not be as large as the weight.
Say there is a cylinder on a ramp and the friction force from the ramp cancels out the parallel component of gravity. Therefore, the cylinder should be in linear equilibrium. However, from the reference point of the center axis of the cylinder, there is a net torque exerted by the friction force. Additionally, there is also a net torque exerted by the gravitational force from the reference point of the point of contact of the cylinder and the ramp. Therefore, it is not in rotational equilibrium and should start to rotate, correct? How is this possible, because if the cylinder starts to roll how can it also be in linear equilibrium?
There is a simple answer to your question: Thank you very much for your response. However, I think you may have misunderstood my question. I was asking what would happen in a case where the frictional force is set to cancel out the parallel component of weight. It seems as if the center of mass cannot move, but the cylinder needs to rotate. Therefore, it would appear as if the only outcome of this situation would be a cylinder rotating in place on a ramp, which does not seem possible. I think that the cylinder would have to roll down the ramp, but I can't see how this would be consistent with linear equilibrium.
I did not misunderstand your question. You cannot simply adjust the friction to be what you want it to be. The cylinder will spin in place. Thanks again but I am still a bit confused. It makes sense that the center of mass will move at a constant velocity while the cylinder is rolling, but how did it acquire that velocity in the first place if I start the cylinder at rest and not sliding as you wrote in the additional thought. So, if you want it to slide down with constant speed, you must give it a shove to start it slipping.
Does mass of an object increase its mass exponentially as it approaches infinitely close to the speed of light? For your question, f is m and q is v. Thus, although m increases without bound as v increases, it does not increase exponentially. Can sustaining enough angular momentum help us stay in a black hole for longer near the event horizon?
If yes, how much energy would be required to sustain it for ten minutes. What do you mean by "in a black hole"? A black hole is a singularity so if you were "in" it you could not have any angular momentum. In any case, I am assuming that your idea is to orbit the black hole so as not to fall in. If you were able to do this, no energy would be required; the earth orbits the sun in a stable orbit with no energy input. However, it is not possible for any object to orbit a black hole anywhere near the Scwartzschild radius because the speed would be too large.
At a radius of 1. This is a result of general relativity. No stable orbits inside this exist and anything inside would fall into the black hole. I have been told that hypothetically speaking when a metal bar or something other object travels in space at the speed of light it shrinks. So my question is if it is correct and why yes or no? First of all, nothing can travel at the speed of light. However, the fact that moving lengths are shorter is not hypothetical, it is simple fact which has been verified by measurements.
It is the result of the special theory of relativity. And, it is not because they appear to be shorter, they actually are shorter. You might look at an earlier answer about length contraction. We have material that generates electricity when exposed to light, or force. Why haven't not found one that does this when exposed to atomic radiation. Imagine almost permanent batteries. There are batteries which get their primary energy from radioactive decay.
Atomic batteries are routinely used in heart pacemakers and low-power requirements in space probes. My question is about the theory of relativity and time dilation. It appears to only work in one direction and I'm not sure why. For example, take a person on earth and compare to a person in a rocket going near the speed of light.
The person on earth observes the rocket man going near light speed and aging slower. The man in the rocket observes earth moving past him near the speed of light except the earth man ages quicker. Congratulations, you have discovered the twin paradox! It is true that the earth man's clock runs slow in the rocket man's frame.
It also is true that the rocket man's clock runs slow in the earth man's frame. But to make a definitive comparison, they must somehow bring their clocks together to compare. In other words, the rocket man has to come back to compare his clock with the earth-bound clock. To get the full explanation of the twin paradox, look on the faq page. Can a ball bounce higher than the height it was dropped? I know that air resistance would slow it down but is it possible? Even if you bounced a ball in a vacuum where there would be no air resistance, it could not bounce higher than the height from which you dropped it.
The only way to achieve this would be to add more energy to the ball, either throw it down rather than drop it or maybe have a little "kick" from its interaction with the floor. An ice-hockey player throws his stick on the ice. The stick translates and rotates. Before it stops, it always rotates and translates - never only rotates or translates. Why do both motions occur simultaneously like this? It actually depends on how it is thrown. S uppose it isn't thrown intentionally in such a way so as to just make it spin or just make it translate.
The motion of a rigid body moving in two dimensions the ice, call it the x-y plane may be broken into two components, motion of the center of mass translation and motion about the center of mass rotation. There are, in your example, no forces in the x - or y -direction once the stick has been thrown if you neglect friction. If the force you throw it with is directed through the center of mass, it will not rotate because there is no torque about the center of mass to get it rotating.
If the net force you throw it with is zero you would need to use two hands to do this it will not translate. If you just randomly grabbed it and threw it, there would be a net force which would result in the center of mass accelerating during the time you were throwing it; and there would be a net torque which would result in the stick having a rotational acceleration during the time you were throwing it. Once you let go, there is no force and no torque on the stick and so both linear and angular momentum would be conserved meaning it would continue moving the way it was moving when you released it.
Suppose a container full of water is kept in a certain area. Let no external force be applied. Now the question is: Will there be an overall circulation of molecules of water? However, in a glass which has been sitting undisturbed for a long time the average velocity is zero, there are always as many moving in any direction as there are moving in the opposite direction. However, you could have a fluid which has a zero average velocity of molecules but they could be circulating like a whirlpool.
If you start such a circulation, it will often last for a relatively long time but, due to viscosity and fluid drag forces, it will eventually die out. This is a brain teaser I have been having trouble with. When the clock is moving towards me, do I observe its hands to be ticking slower, faster, or at the same rate compared to the rate of ticks that I observe when it's moving away from me?
A clock will appear to run faster than yours when moving toward you. A clock will appear to run slower than yours when moving away from you. But that clock is actually running more slowly than yours in both directions and not by the same factor as it appears to run when going away from you. I think you will understand why is you look at earlier answers to a particular faq on the faq page. Keep in mind that moving clocks run slow, they do not just appear to run slow; how things are and how things seem are often not the same.
Many Science Fiction ships have for protection a shield that stops projectiles and saves the ship from a lethal impact. Such an example would be the energy shields possessed by the faction known as Covenant from Halo. So given the laws of Newton and the third law about there always being an equal force countering the force that was exerted first, wouldn't this just mean that whenever the energy shield takes a hit by a projectile, the force would ''travel'' from the shield to whatever generator generates the shield. They're 30ft long and around 7ft wide.
So they have a lot of force and momentum behind them. So wouldn't an impact like this just cause the shield generator to be violently thrown off its attachments and ''fly off'' through the compartments of the ship destroying a lot of the ship? When this hits something, it will certainly exert a force, but the magnitude of that force will depend on how long it took to stop. I have no idea how big it is, but suppose it has a radius of 10 km from the ship; I will think of it as very flexible and suppose that it stretches inward just stopping before it hits the ship.
I also will assume that the ship is much more massive than the slug; elsewise how could a comparably-sized ship carry a bunch of them and fire them without huge recoil? You are certainly right, this very large force will be felt by the ship because of Newton's third law.
If the shield were very rigid, it would be catastrophe for the ship. I have never played these games but I expect the shield is shown as stopping the slug almost instantly. A little should be said about the other end, launching the slug in the first place. In this case, unless the cannon has a 10 km barrel, the recoil force on the ship will be huge.
If I were to drop two round balls of different mass under water would they both fall to the bottom at the same velocity or would one reach the bottom first? The forces on a ball are its own weight mg down; the buoyant force B up which would be equal in magnitude to the weight of an equal volume of water; and the drag force f up which would depend on the size the ball and its speed.
The larger the mass, the larger the terminal velocity. Without specifying the the sizes of the balls, your question cannot be answered. If they had identical sizes, the heavier ball would reach the bottom first because it would have a larger terminal velocity.
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If you performed the double slit experiment in outer space and were observing the electron particles would you get a diffraction pattern or two rows of particles. Does the earth's atmosphere have any effect on the experiment? Any electron diffraction experiment is always performed in a vacuum. The range of the electrons in air is short enough that it would entirely ruin any experiment you tried to do.
Electrons interact strongly with any atoms in their vicinity. In outer space you would have a vacuum so you would see a diffraction pattern. The box is pretty tall. I figure there might be a quick, static "tip test" with a combination pull gauge, inclinometer and scale, but my math skills are primitive. Is there a simple way to ascertain whether, for a given object, a target stability threshold is met? There is an earlier answer about a bicycle making a turn. It would be helpful for you to read that first. The picture above shows all the forces on the box plus trailer: W is the weight and the green x is the center of gravity COG of the box plus trailer; f 1 and f 2 are the frictional forces exerted by the road on the inside and outside wheels respectively; N 1 and N 2 are the normal forces exerted by the road on the inside and outside wheels respectively; the center of gravity of the box plus trailer is a distance H above the road and the wheel base is 2 L with the center of gravity halfway between the wheels.
If you work this out, you find the normal forces which are indicative of the weight the wheels support: A few things to note are:. Now we come to your question. You first want the maximum speed without tipping. Be sure to note that the assumptions of a level road not banked and wheels not slipping are used in my calculations. Also be sure to note that W is the weight of both box and trailer and 2 L is the wheel base, not the box width. One more thing is that you might not know how to find the COG of the trailer plus box.
If a 20 pound rock and pound rock or drop from feet which will hit the ground first. If air drag is neglected, they would hit simultaneously. If air drag is considered, it would depend on the geometry of the two objects. If they have identical shapes and sizes, the heavier rock would hit first; otherwise, you would need to know the shape and size of each to calculate the times to fall. See the faq page. A starship pilot wants to set her spaceship to light speed but the crew and passengers can only endure a force up to 1.
Assuming the pilot can maintain a constant rate of acceleration, what is the minimum time she can safely achieve light speed? This question completely ignores special relativity. It is impossible to go as fast as the speed of light. Furthermore, acceleration is not really a useful quantity in special relativity and you must use special relativity when speeds become comparable to the speed of light.
I have earlier worked out the velocity of something which would correspond to occupants of your spaceship experiencing a force equal to their own weight due to the acceleration which I will adapt to your case later. See the graph above. First, though, I will work out the incorrect Newtonian calculation which is presumably what you want.
To make this your problem, we simply replace g by 1. Why do wavefunctions need to be normalized? So that the absolute square of the wave function can be interpreted as a probability density. Will a heavier ball roll down a small slope faster than a lighter ball? Or will a lighter ball roll down a small slope faster than a heavier ball?
If both are solid balls of the same radius but of different masses, they will take equal times if air drag is neglected as might be appropriate for a "small slope". If they get going fast enough that air drag becomes important, the heavier ball will win the race. During refraction why does a light ray bend This is not simple. The following situation occured with my son, would you mind sending me the formula or the resulting impact force? Car A kg rear-ends car B kg. Car B Automatic gear is on park is shoved 2 meters 6. What is the impact force on Car B Tons?
No way to calculate this without much more information. See the FAQ page for other impossible to calculate the force situations. Thank you very much for your reply. Tones with just the weight of car one and 2 meters of course it refers to 1 car hitting a tree, but the force of impact must be close. Does it sound reasonable to you? Maybe I could make a very rough estimate if I knew whether the incoming car was skidding, if the pavement was dry asphalt, was there any notable compression of the cars like a bumper moved in by 2 cm?
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Would a speed of about 15 mph be reasonable? Thank you very much for tryng to help find the force of impact. The incoming A car was shoved 1meter neutral gear no brakes before hitting B and Car B in Park was shoved 2 meters into Car C which was shoved 1 meter into Car D - B car rear bumper was compressed by 25cm lower body frame steel bent 10cm - The estimated speed 25 mph of impact Car 03 A to Car 04 B.
If I understand things correctly, it really is impossible now to do any meaningful calculations. I had thought from your earlier question that car B was at rest after going 2 m but now there are far too many unknowns. With two cars there was a possibility that I could have done a very rough estimate, with this situation it is truly hopeless. That's why I simplified it to 2 cars. Stop means B hit C but this is irrelavant to a rough estimate Dry asphalt Car B 25 cm rear bumper compression Without making it complicated with the compounded forces from other cars etc, all I would like to have a rough idea is, what aproximatly was the force of impact exerted from Car A onto car B.
Do you that is possible to roughly calculate the force of impact Tons? Is a correction due? Geneva-based chipmaker STMicroelectronics has moved most of its six-inch wafer production. The deals are sale-and-leaseback agreements, with both vendors taking a long lease on the properties. Infosys profits up, but earnings forecast down -AFP INFOSYS Technologies beat expectations with a per-cent jump in first-quarter profit yesterday, but cut its fullyear forecast as a surging rupee hit the value of dollar-billed exports.
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