Question

You can move a brick easily by pushing it with your foot on a smooth floor, but, if you kick it, then your foot is hurt. Why?

Answer 1

1. When we kick the brick the time for which force is imparted is less. So, the rate of change of momentum is large in a short time. That's why the impact will be large.
2. Therefore, the rate of change of momentum of the brick is large.
3. So, a large reaction force is applied back by the brick on the foot. So, force hurt our foot.