$A$ truck starting from rest moves with an acceleration of $5\,m/s^2$ for $1\,sec$ and then moves with constant velocity. The velocity w.r.t. ground v/s time graph for the block in the truck is (Assume that the block does not fall off the truck and the coefficient of friction $\mu = 0.2$):

$A$ constant force $F$ is applied in the horizontal direction as shown. If the contact force between $M$ and $m$ is $N$ and the contact force between $m$ and $M'$ is $N'$,then:

State whether the following statements are true or false:
$(a)$ $A$ necessary condition for equilibrium is that the acceleration must be zero.
$(b)$ Centripetal force is always in the opposite direction of centrifugal force.
$(c)$ $A$ man is at rest on a perfectly smooth ice surface in the middle of a pond. He can reach the shore by using Newton's first law.
$(d)$ An object is in equilibrium only if it is at rest.

$A$ person is managing to be at rest between two vertical walls by pressing one wall with his hands and feet and the second wall with his back. The coefficient of friction is $0.5$ between his body and the walls. If the force with which the person pushes the walls is $500 \ N$,then the mass of the person is (Take $g = 10 \ m \ s^{-2}$) (in $kg$)

What is the ratio of the accelerations of both systems?

$A$ block of mass $m$ is suspended by a light thread from an elevator. The elevator is accelerating upward with uniform acceleration $a$. The work done by tension on the block during $t$ seconds is $(u = 0)$.