When does newton's second law take the form of f=ma?
The Newton's second law of motion is often applied in our everyday life. You might have noticed that while catching a fast moving cricket ball, a fielder gradually pulls his hands backward. Do you why? He do this so as to increase the time during which the high velocity of the moving ball decreases to zero. Thus the impact of the ball is reduced.
Let us take another case also. A high jump athlete falls either on a cushioned bed or on a sand bed. This reduces the change in momentum and hence the force also.