Lakhmir Singh and Manjit Kaur Solutions for Chapter: Work and Energy, Exercise 18: Long Answer Type Questions

Explain the transformation of energy in the following cases: a stone dropped from the roof of a building.

Explain how, the total energy of a swinging pendulum at any instant of time remains conserved. Illustrate your answer with the help of a labelled diagram.

What is the meaning of the symbol $\mathrm{kWh}$? What quantity does it represent?

How much electric energy in $\mathrm{kWh}$ is consumed by an electrical appliance of $1000$ watts when it is switched on for $60$ minutes?

Derive the relation between commercial unit of energy $\left(\mathrm{k}\mathrm{W}\mathrm{h}\right)$ and SI unit of energy (joule).

A certain household consumes $650$ units of electricity in a month. How much is this electricity in joules?

Define power. Give the SI unit of power.

A boy weighing $40 \mathrm{k}\mathrm{g}$ carries a box weighing $20 \mathrm{k}\mathrm{g}$ to the top of a building $15 \mathrm{m}$ high in $25 \mathrm{s}$. Calculate the power, $(\mathrm{g}=10 \mathrm{m}/{\mathrm{s}}^2)$