$A$ block of mass $m$ is kept in an elevator which starts moving downward with an acceleration $a$ as shown in the figure. The block is observed by two observers $A$ and $B$ for a time interval $t_0$. The observer $B$ is on the ground (inertial frame). What is the work done by the pseudo force on the block as observed by observer $B$?

$A$ block can slide on a smooth inclined plane of inclination $\theta$ kept on the floor of a lift. When the lift is descending with a retardation $a$,the acceleration of the block relative to the incline is

Inside a horizontally moving box,an experimenter finds that when an object is placed on a smooth horizontal table and is released,it moves with an acceleration of $10\,m/s^2$. In this box,if a $1\,kg$ body is suspended with a light string,the tension in the string in the equilibrium position (with respect to the experimenter) will be $.........\,N$. (Take $g = 10\,m/s^2$)

$A$ block of mass $m$ is placed on a smooth inclined wedge $ABC$ of inclination $\theta$ as shown in the figure. The wedge is given an acceleration $a$ towards the right. The relation between $a$ and $\theta$ for the block to remain stationary on the wedge is

$A$ lift is moving downwards with an acceleration equal to the acceleration due to gravity. $A$ body of mass $m$ kept on the floor of the lift is pulled horizontally. If the coefficient of friction is $\mu$,then the frictional resistance offered by the body is:

$A$ mass is hanging on a spring balance which is kept in a lift. The lift ascends with an acceleration. The spring balance will show in its readings: