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Friction Paradox? (physics problem)?
Imagine a block being pushed up a slope at constant acceleration. There is a force pushing on it horizontally which accordingly has components in the y and x axis. There is friction on the slope, dependent on the normal force. This is where the paradox comes in. If the friction is dependent on the normal force, then while you push, you effectively increase the normal force and thereby increase the friction, increasing the force necessary to maintain constant acceleration and increasing the friction and force on to infinity. Someone point out my bad logic please.
2 Answers
- MadhukarLv 71 decade agoFavorite Answer
When you push, it is true that the normal force increases and hence the friction, but that is a one time process. It does not continue to keep on increasing with time. The net force up the slope = component of the applied force up the slope less the frictional force due to increased frictional force and this difference remains constant during the motion as the acceleration is constant as sgtated by you in the first line. So your logic that the frictional force keeps on increasing indefinitely is incorrect.
- NashLv 61 decade ago
I'm not sure if I see a paradox. But there may be something I am missing.
What you seem to be saying is that you can't accelerate something infinitely. It goes without saying that even without any friction, you would have to supply a steady force to accelerate indefinitely. And with a steady friction, you would need an ever increasing force to accelerate indefinitely.
In some real world applications, the friction coefficient will drop as the block heats up. So you may in some instances get away with a steady force causing acceleration. But I don't think that's what your talking about.
