$A$ body is moving with constant speed over a frictionless surface. What is the work done by the weight of the body?

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

How is work done by a force measured? $A$ porter lifts a luggage of $20 \, kg$ from the ground and puts it on his head $1.7 \, m$ above the ground. Find the work done by the porter on the luggage. $(g = 10 \, m s^{-2})$

$A$ box of mass $10 \, kg$ is placed at point $A$ on a horizontal surface. It is moved to point $B$,which is at a distance of $2 \, m$ from $A$. If the line joining $A$ and $B$ is horizontal,find the work done by the gravitational force on the box. Justify your answer. $(g = 10 \, m s^{-2})$ (in $, J$)

The work done in lifting a box onto a platform does not depend upon how fast it is lifted up. Explain your answer giving proper reasoning.

$A$ person holds a bundle of hay over his head for $30$ minutes and gets tired. Has he done some work or not? Justify your answer.