Work

Johnny and his sister Jane race up a hill. Johnny weighs twice as much as Jane and takes twice the time as long as Jane to reach the top. Compared to Jane:

The amount of work done by the centripetal force when the earth revolves around the sun is _____.

(Choose from zero/non-zero)

Force of $4 \mathrm{N}$ is applied on a body of mass $20 \mathrm{kg}$. Find the work done in Joules in $3$rd second.

A man spends $6.4 \mathrm{k} \mathrm{J}$ energy in displacing a body by$64 \mathrm{m}$ in the direction in which he applies force, in $2.5 \mathrm{s}$. The force applied and the power spent (in hp) by the man respectively are:

An electric motor of power $100 \mathrm{W}$ is used to drive the stirrer in a water bath. If $50\%$ of the energy supplied to the motor is spent in stirring the water, calculate the work done (in joules) on water in one minute.

Whenever a force is applied, work is done.

Force acting opposite to the direction of motion of a body does negative work on it.

The power of heart which beats $72$ times in a minute is $1.2 \mathrm{kW}$. Calculate the work done (in joules) by the heart for each heartbeat.

Force and displacement are inclined to each other at an angle of $120°$. Will the work done be positive or negative?

A man pulls a bucket out of a well by means of a rope. The work done by the man is

The work done by a force is _____ (positive/ negative/ zero) if the displacement in the direction of the force increases.

Describe the properties of work done.

A body is displaced by $10 \mathrm{m}$ when maximum work of $200 \mathrm{J}$ is done on it. Calculate the force acting on this body in newton.

The system of two masses $2 \mathrm{kg}$ and $3 \mathrm{kg}$ shown in the figure is released from rest. The work done on $3 \mathrm{kg}$ block by the force of gravity during first $2 \mathrm{seconds}$ of its motion is $\left(g\mathit{=}10 \mathrm{m} {\mathrm{s}}^{-2}\right)$

The force acting on the block is $10\sqrt{2} \mathrm{N}$ with an angle $135°.$ Calculate the work done when the displacement is $\mathrm{\Delta x}=5 \mathrm{m}$

A gardener pulls a lawn roller along the ground through a distance of $20 \mathrm{m}.$ If he applies a force of $20 \mathrm{kg} \mathrm{wt}$ in a direction inclined at $60°$ to the ground, find the work done by him. (Take $g=10 \mathrm{m} {\mathrm{s}}^{-2}$):

If this lift is moving downward with constant velocity $20 \mathrm{m} {\mathrm{s}}^{-1},$ find work done by tension in $2 \sec$:-