A ball of mass m moves with speed $v$ and it strikes normally with a wall and reflected back normally, if its time of contact with wall is $t$ then find force exerted by ball on wall

A body of mass $m$ collides against a wall with a velocity $v$ and rebounds with the same speed. Its change of momentum is

A particle of mass m moving with a velocity $u$ makes an elastic one dimensional collision with a stationary particle of mass $m$ establishing a contact with it for extremely small time $T$. Their force of contact increases from zero to $F_0$ linearly in time $\frac{T}{4}$, remains constant for a further time $\frac{T}{2}$ and decreases linearly from  $F_0$  to zero in further time $\frac{T}{4}$ as shown. The magnitude possessed by $F_0$  is