How much force must be applied to maintain a constant velocity?

Question

If the kinetic friction force acting on a sliding crate has a magnitude of 120N. How much force must be applied to maintain a constant velocity?

Answer 1

In my Opinion it should be 120N force opposite to the direction of kinetic frictional force ...
coz to maintain constant velocity the forces must be in equillibrium ...

Answer 2

As per newton first law - a moving object will keep moving at the same speed or stationary object will remain stationary if and only if there is no external force is applied. Now in this case external friction is 120 N so a force of 120 N to be applied to counter the friction so that total external force is zero and constant velocity is maintained.

Comments

nicely explained .... hatsoff .