A particle of mass $m$ moving with velocity $u$ makes an elastic one dimensional collision with a stationary particle of mass $m$. They are in contact for a very short time $T$. Their force of interaction increases from zero to $F_0$ linearly in time $T/2$, and decreases linearly to zero in further time $T/2$. The magnitude of $F_0$ is

A ball of mass $150\,g$ starts moving with an acceleration of $20m/{s^2}$. When hit by a force, which acts on it for $0.1\, sec$. The impulsive force is …….. $N-s$

The momentum is most closely related to