$A$ man weighing $50 \, kg$ lifts a weight of $30 \, kg$ to the top of a building $10 \, m$ high. Find the work done by him. (Take $g = 9.8 \, m s^{-2}$) (in $, J$)

Does work done depend upon the velocity of the body?

$A$ porter moving vertically upstairs with a load on his head does work. Why?

$A$ boy pushes the wall in the class for five minutes but the wall does not move. Another boy pushes the chair from the front to the back side of the class. In which case,more work is done?

In each of the following cases,a force $F$ is acting on an object of mass $m$. The direction of displacement is from west to east,shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative $(-ve)$,positive $(+ve)$,or zero $(0)$.

In a tug-of-war,one team gives way to the other. What work is being done and by whom?