A person starts from rest and begins to run. The runner puts a certain momentum into himself. What is the momentum of ground ? And the runner puts a certain amount of kinetic energy into himself. What is the kinetic energy of the ground ?

Explanation

Here two cases arise.
Case - I : In view of the observer, ground has no velocity. Hence the momentum and kinetic energy of the ground will be zero.
Case - II : In view of the runner, ground has a velocity equal to the velocity of the runner.
1) The momentum of ground is equal to the momentum of the runner in magnitude but opposite in direction.
The K.E. of ground is also equal to the K.E. of the runner in magnitude but oppostite in direction.