Question

When you push something heavy ,the restance you fell decrease as the body stars moving . Explain what happens .

Answer 1

In the real world, friction exists. There are two phenomena which are occurring, static and kinetic friction. Static friction occurs when the body is at rest and kinetic friction occurs when the body is in motion. Kinetic friction is usually less than static friction, and therefore more force is required to overcome static friction.
When we push something which is stationary, we have to overcome static friction so we have to apply large force

When body starts to move,there is no static friction. Here only kinetic friction is present which is less than static friction. So we have to apply less amount of force to overcome it

Resistance means the friction, here static friction changes to kinetic friction. That is what happening here