$A$ 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 $t_0$. According to observer $B$,the net work done on the block is

If a person is pushing a box inside a moving train,the work done in the frame of the earth will be: (where $\vec{s}$ is the displacement of the box in the train and $\vec{s}_0$ is the displacement of the train relative to the ground)

$A$ body constrained to move along the $z$-axis of a coordinate system is subject to a constant force $F$ given by $F = -\hat{i} + 2\hat{j} + 3\hat{k} \text{ N}$,where $\hat{i}, \hat{j}, \hat{k}$ are unit vectors along the $x, y,$ and $z$-axes of the system respectively. What is the work done (in $J$) by this force in moving the body a distance of $4 \text{ m}$ along the $z$-axis?

If $\vec{F}$ and $\vec{S}$ are force and displacement respectively,and the work done by them is zero,then:

$A$ chain of mass $M$ and length $L$ is hanging from the edge of a table such that one-third of its length is hanging off the edge. The work done to pull the hanging part onto the table is:

$A$ force of $5 \ N$ acts on a stationary body of mass $15 \ kg$. What is the work done during the first second of motion?