$A$ man pushes a wall and fails to displace it. He does:

Work done in time $t$ on a body of mass $m$ which is accelerated from rest to a speed $v$ in time $t_1$ as a function of time $t$ is given by

$A$ force $\vec{F} = (5 \hat{\imath} - 2 \hat{\jmath} + 3 \hat{k}) \text{ N}$ acts on a body of mass $2 \text{ kg}$ and displaces it from position $\vec{r_1} = (3 \hat{\imath} + 2 \hat{\jmath} - \hat{k}) \text{ m}$ to $\vec{r_2} = (6 \hat{\imath} - \hat{\jmath} + 4 \hat{k}) \text{ m}$. The work done is: (in $\text{ J}$)

$A$ porter lifts a heavy suitcase of mass $80\, \text{kg}$ and at the destination lowers it down by a distance of $80\, \text{cm}$ with a constant velocity. Calculate the work done by the porter in lowering the suitcase. (Take $g = 9.8\, \text{m/s}^2$) (In $\text{J}$)

The work done in moving an object from the origin to a point whose position vector is $\vec{r} = 3 \hat{i} + 2 \hat{j} - 5 \hat{k}$ by a force $\vec{F} = 2 \hat{i} - \hat{j} - \hat{k}$ is:

$A$ 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