When a coil spring is compressed,the work is done on the spring. The elastic potential energy:

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. $(g = 10 \, m s^{-2})$

$A$ man of mass $60 \, kg$ runs up a flight of $30$ steps in $40 \, s$. If each step is $20 \, cm$ high,calculate the power of the man.

$A$ car is accelerated on a levelled road and attains a velocity $4$ times of its initial velocity. In this process,the potential energy of the car

What is power? How do you differentiate kilowatt from kilowatt hour? The Jog Falls in Karnataka state are nearly $20 \, m$ high. $2000$ tonnes of water falls from it in a minute. Calculate the equivalent power if all this energy can be utilized? $(g = 10 \, m \, s^{-2})$

Is it possible that a body be in accelerated motion under a force acting on the body,yet no work is being done by the force? Explain your answer giving a suitable example.