An object of mass $'m'$ is being moved with a constant velocity under the action of an applied force of $2\, {N}$ along a frictionless surface with following surface profile.

The correct applied force vs distance graph will be:

$100$ balls each of mass moving with speed $v$ simultaneously strike a wall normally and reflected back with same speed, in time $t s$. The total force exerted by the balls on the wall is

A body is accelerated by applying a force of $30\,N$. The change in the momentum of the body after $2\,sec$ is ............ $kg-m/s$ 

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

$Assertion$ : A rocket moves forward by pushing the surrounding air backwards.

$Reason$ : It derives the necessary thrust to move forward according to Newton’s third law of motion