You push a heavy crate. At first it doesn't move. You push harder, and it finally starts to move, but you still have to exert some force to keep it moving at a constant velocity. Explain.

Explained below.

Explanation:

Newton's first law of motion states that an object will continue in its present state of rest or continue with constant speed in a straight line except it is acted upon by an external force.

For every object in motion or at rest there is a force of friction that tries to resist its motion or prevent it from moving with constant velocity.

Now, to push it from rest you will need to apply a force large enough to overcome its static friction. Now, after that initial motion, smaller forces will have to be applied to overcome what is called sliding friction that prevents the crate from sliding which will affect the constant velocity.

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