Explain why?
(a) a horse cannot pull a cart and run in empty space.
(b) passengers are thrown forward from their seats when a speeding bus tops suddenly
(c) It is easier to pull a lawn mower than to push it.
(d)a cricketer moves his hands backwards while holding a catch

Explanation

(a) The horse-cart system has no external force in empty space. The mutual forces between the horse and the cart cancel each other (Third Law). On the ground the contack force between the system and the ground (friction) causes their motion from rest.
(b) Due to inertia of parts of the body which are not directly in contact with the seat.
(c) A lawn mover is pulled or pushed by applying force at an angle. When we push, the normal force (N) must be more than its weight, for equilibrium in the vertical direction. This results in greater fricition `f(fpropN)` and, therefore, a greater applied force to move. Just the opposite happends while pulling.
(d) To reduce the rate of change of momentum and hence to reduce the force necessary to stop the ball.