Kerala Board Solutions for Chapter: Work, Energy and Power, Exercise 5: Let us assess

Say whether the work done by the force acting in the direction of motion on an object which is moving along a plane surface is positive work or negative work.

How much joule is $1 \mathrm{kW} \mathrm{h}$?

Find out the work done against the gravitational force when a child is standing still with a bundle of books of mass $5 \mathrm{kg}$.

Find out the work done against the gravitational force when a child is carrying a bundle of books of mass $5 \mathrm{kg}$, she travels $1 \mathrm{m}$along a plane surface with a speed $5 \mathrm{m}/\mathrm{s}$.

Find out the work done (in joules) against the gravitational force when the bundle of books with mass $5 \mathrm{kg}$ is lifted onto the top of a cupboard having $1 \mathrm{m}$ height ($g=10 \mathrm{m}/{\mathrm{s}}^2$).

A ball of mass $0.4 \mathrm{kg}$is thrown vertically upward with a velocity $14 \mathrm{m}/\mathrm{s}$. Calculate its kinetic energy and potential energy after $1 \mathrm{s}$. (Take $g=10 \mathrm{m}/{\mathrm{s}}^2$).

An object of mass $1000 \mathrm{kg}$ is travelling with a velocity $72 \mathrm{km}/\mathrm{h}$. Calculate the work done to bring it to rest.

Estimate the work done (in joules) on an object of mass $80 \mathrm{kg}$ to change its velocity from $5 \mathrm{m}/\mathrm{s}$ to $10 \mathrm{m}/\mathrm{s}$.