A P Shreelatha and Neetu Singh Solutions for Chapter: Work and Energy, Exercise 6: EXERCISES

A lift carries $5$ persons with an average mass of $60 \mathrm{kg}$ to a height of $27 \mathrm{m}$ in $9$ seconds at a constant speed. What is the power (in watt) of the lift? Take $g=9.8 \mathrm{m} {\mathrm{s}}^{-2}$
(Solution should contain only magnitude of power).

A person lifts $80 \mathrm{kg}$ suitcase from the ground and puts on his head $2 \mathrm{m}$ above the ground. Calculate the work done by the person.

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

A horizontal force of $50 \mathrm{N}$ displaces an object of mass $100 \mathrm{kg}$. Calculate the work done by the force in $8$ seconds.

A $500 \mathrm{W}$ electric bulb lighted for $2$ hours everyday and an electric motor of $0.5$ horse power is used for $2$ hours everyday. Calculate the cost of using the bulb and the motor for $30$ days, if the cost of electrical energy is three rupees per unit.

An electric heater of $1000 \mathrm{W}$ is used everyday for $70$ minutes. Calculate the units of electrical energy this heater will consume in $30$ days of use.

A bag of wheat weighing $8 \mathrm{kg}$ is lifted through a height of $12 \mathrm{m}$ in $5$ seconds with a constant velocity. Calculate the power developed during the process.

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 $\cos 45°=0 .7071)$