How Can Kinetic Energy Change with Zero Net Work?

AI Thread Summary
The discussion centers on the confusion regarding the work-energy theorem, specifically how kinetic energy can change while net work is zero. When a box is pushed on a horizontal surface with a force equal to friction, it moves at constant velocity, indicating that the net force is zero and thus the net work done is also zero. However, the box initially required additional force to overcome static friction, leading to a change in kinetic energy as it transitioned from rest to motion. This initial force does perform work, but once the box reaches constant velocity, the work done becomes zero. Therefore, while the kinetic energy changes during the initial acceleration, the net work done during constant velocity is indeed zero.
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Homework Statement


There is something I don't understand in work energy theorem
If we push on a box on a horizontal surface with force F to cause it to move with displacement x with constant velocity that means the force by friction is equal to F right? so the total work is the net force times the displacement which is zero
but the box was initially at rest then it is moving with constant velocity so there is change in kinetic energy
so how can there be change in kinetic energy with zero work?


Homework Equations





The Attempt at a Solution

 
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when the body is moving with constant velocity, there is no change in constant velocity.

Also, for the body to start from rest, it needs a little more force (if you notice that coefficient of static friction is more than kinetic)...
 
Then in the time interval from just before you applied the force till it moved with constant velocity we can't actually say the total work is 0 right?
 
exactly.
 

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