$A$ body of mass $100 \, g$ is rotating in a circular path of radius $r$ with constant velocity. The work done in one complete revolution is

$A$ chain of mass $m$ and length $\ell$ is held on a frictionless table in such a way that its $\frac{2 \ell}{5}$ part is hanging below the edge of the table. Find the work done to pull the hanging part of the chain up onto the table.

$A$ block of mass $2 \,kg$ is pulled at a constant speed with a taut rope along a frictionless plane that is inclined at $30^{\circ}$. Then the work done by the tension in the rope in pulling it a distance $4 \,m$ along the inclined plane in joule is (acceleration due to gravity $= 10 \,ms^{-2}$)

$A$ force of $(3\,\hat i + 4\,\hat j) \, N$ acts on a body and displaces it by $(3\,\hat i + 4\,\hat j) \, m$. The work done by the force is .............. $J$.

$A$ small particle moves to position $5 \hat{i}-2 \hat{j}+\hat{k}$ from its initial position $2 \hat{i}+3 \hat{j}-4 \hat{k}$ under the action of force $5 \hat{i}+2 \hat{j}+7 \hat{k} \text{ N}$. The value of work done will be $............ \text{ J}$.

$A$ 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