Work

What is gravitational potential energy? Derive its equation.

Explain the different conditions for work done such as the minimum, maximum and zero work done.

What is work done by friction ?

If the _____ of an object is zero, work done on it is also zero.

In case of negative work the angle between the force and displacement is

The SI unit of work is :

In case of negative work the angle between the force and displacement is

A force of $200 \mathrm{N}$ acting at an angle of $45°$ to the horizontal does a work of $45000 \mathrm{J}$. Calculate the displacement caused by the force in horizontal direction. (Take $\cos 45°=0 .7071)$

Unit of work is

A girl weighing $400 \mathrm{N}$ climbs a vertical ladder. If the value of $g$ be $10 \raisebox{1ex}{$\mathrm{m}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{s}}^2$}\right.$, the work done by her after climbing $2 \mathrm{m}$ will be:

The work done on an object does not depend on the:

A girl is carrying a school bag of $3 \mathrm{k}\mathrm{g}$ mass on her back and moves $200 \mathrm{m}$ on a levelled road. If the value of $\mathrm{g}$ be $10 \raisebox{1ex}{$\mathrm{m}$}\!\left/ \!\raisebox{-1ex}{${\mathrm{s}}^2$}\right.$, the work done by the girl against the gravitational force will be:

In case of negative work, the angle between the force and displacement is:

In each of the following a force, $\mathrm{F}$ 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, positive or zero.

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.

What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer. 

A mass of $10 \mathrm{kg}$ is at a point $\mathrm{A}$ on a table. It is moved to a point $\mathrm{B}$. If the line joining $\mathrm{A}$ and $\mathrm{B}$ is horizontal, what is the work done on the object by the gravitational force? Explain your answer.

Certain force acting on a $20 \mathrm{kg}$ mass changes its velocity from $5 \mathrm{m} {\mathrm{s}}^{-1}$ to $2 \mathrm{m} {\mathrm{s}}^{-1}$. Calculate the work done by the force.

A pair of bullocks exert a force of $140 \mathrm{N}$ on a plough. The field being ploughed is $15 \mathrm{m}$ long. How much work is done in ploughing the length of the field?

Define $1 \mathrm{J}$ of work.