Question

a cart has to pull harder during the start of motion than later.explain?

Answer 1

during the start of the motion the cart has to overcome the static friction and when the cart is moving there is only the rolling friction causing motion and it is easy to pull as it has some initial velocity

Answer 2

At the start, the cart has to overcome friction between the wheels and the ground ( static friction). But later, the static friction has been overcame so it glides on the ground without much effort.