Question

If you push on a heavy box which is at rest, it requires some force F to start its motion.
However, once the box is sliding, it requires a smaller force to maintain its motion. Why is this so?

Answer 1

Answer:

this is becoz of inertia !.

a body resist any change in motion hence it is easy to maintain its state

good day

Answer 2

Answer:limiting friction

Explanation:because of limiting friction

When it is in static let say 0 N its kinetic friction is 0 and limiting friction is also 0 force applied 0 when froce is given 20 N and static friction becomes 20 N then kinetic friction remains 0 and limiting friction also when it is given 70 N its tends to move and then limiting friction changes to 70 N when force applied to 80 N then it starts moving then the kinetic friction will be less then the given force so (80-50)=30 N .so it is because of limiting friction when the box starts moving it gain its kinetic friction which makes the force to apply less .