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Physics/Acceleration of Moving Objects


Does it take more force to accelerate a moving object in the same direction ; as compared to accelerating an object that is not moving,say on a track. The moving object lets say  is moving on a track, and the whole track is accelerated forward while the object continues to maintain its constant speed in relation to the track. Would it take more force to accelerate the track with the object moving on it?

Please forgive my delay in responding -- it's the only way I can think of, to ensure I am not assisting with academic work, of which homework is just a small part. Also, as I am unable to determine the veracity of what people post, I can not know whether or not a question involves academic work.

> Does it take more force to accelerate

There are ONLY two things that determine the degree of acceleration of any object, in any place, under any circumstances: the net force on the object and that total object's mass.

Note, however, a key word in the phrase above: "NET force."
If I tap a hockey puck on slick ice, it will accelerate quite easily, because there is almost no force on the puck other than the external force I supply. On the other hand, if I give the exact same tap to the exact same puck on sand paper, there will be almost no acceleration. Why? Because there is a friction force between the puck and the sand paper, which negates the force of my tapping. Thus, the NET force is zero -- meaning no acceleration.

If you exert a force on a track, its acceleration will (again) be based on two things: the NET force on the track, and the mass of the track. If there is NO OTHER FORCE on the track, then the calculation is easy. If, however, there is a friction force between the track and an object on the track, then that friction force will (to some extent) negate the external force you are exerting on the track. Thus, if there is an object on the track, the friction between that object and the track will (to some extent) negate the force you are exerting on the track, causing a smaller NET force, causing a smaller acceleration.

And if that doesn't make things worse, there are TWO kinds of friction: static and moving. The former is the friction force when an object is standing still on something, and it is the amount of friction force you must overcome to get the object moving in the first place.
Moving friction, on the other hand, is the force you must overcome to keep the object moving -- if you fail to overcome it, then the object will have ONLY that moving friction force on it, and it will change it's velocity. In other words, it will have negative acceleration.

Moving friction is generally a smaller force than static friction, but the two can be comparable. So it's generally impossible to know ahead of time how much larger is the moving friction over the static friction; the two must be measured.


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I can help with understanding physics that does not involve eggs. I will NOT help with academic or professional questions, which are NOT limited only to homework. Please do not waste your time by asking a question that comes out of ANY kind of academic, professional, or business matters.


Have been fascinated by physical laws ever since I learned, at age seven, that magnets work under water. My study continued through college and has not ceased even after I retired.

B.A. in Physics (with honors) from University of California at Berkeley.M.A. in Physics (with honors) from University of Texas Austin.

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