Newtonian Mechanics – How Kinetic Friction Stops a Sliding Object

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The kinetic friction is constant. So if say, I apply a force of 20N on an object and the kinetic friction is 13N, then how does the object stop moving after some seconds.
I believe that kinetic friction is constant, it cannot increase more than the applied force by changing its value on its own like static friction?

So does the object stop because the effect of applied force decreases over time? How does this happen due to kinetic friction (keeping in mind kinetic friction is constant – has a fixed value)? How does this work?

How does an object remain balanced on a frictionless surface and keep moving with a constant velocity without any friction to balance the forces (the resultant net force is equal to 0.)

Best Answer

Imagine you throw a ball vertically upward against the force of gravity , the ball would move some distance vertically and then stop due to force of gravity.

When you throw the ball , you exert force on the ball which is obviously greater than gravitational pull. But after throwing the ball the force applied by you become zero , so why does the ball travel some distance and then stop?

The answer: The instant you throw the ball , it gains some acceleration due to your applied force which is indeed greater than gravitational force. Suppose the initial velocity the ball will get due to applied force is 50m/s . It will take 5 seconds to gravitational force to stop the ball ( accelration due to gravity = 10 m/s²).

This is what happens in the case described by you. Kinetic friction will take some time to stop the object since the accelration provided by you was bigger than the accelration(retardation) of kinetic friction.

Hope this helps

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