Dhiren M Doshi Solutions for Chapter: Work and Energy, Exercise 6: Check Your Progress

In spite of the SI unit of electrical energy, there is a need for the commercial unit of energy. Give reasons.

Define one $\text{kilowatt-hour}$.

How is electricity bill calculated?

A water pump raises $50 \mathrm{kg}$ of water through a height of $25 \mathrm{m}$ in $5 \mathrm{s}$. Calculate the power which the pump supplies. (take $\mathrm{g}=10 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{${\text{s}}^2$}\right.$)

Calculate the power of a pump which can lift $100 \mathrm{kg}$ of water stored in a water tank at a height of $19 \mathrm{m} \mathrm{in} 25 \mathrm{s}.$ (take $\mathrm{g}=10 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{${\text{s}}^2$}\right.$)

A boy of mass $50 \mathrm{kg}$ runs up a staircase of $60$steps in $9 \mathrm{s}$. If the height  of each is $15 \mathrm{cm}$, find his power. (take $\mathrm{g}=10 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{${\text{s}}^2$}\right.$) 

If an electric bulb of $100 \mathrm{W}$ is lighted for $20$ hours, how much electrical energy will be consumed? Also find the cost, if $1$ unit costs ₹$4$.

If an electric bulb of $60 \mathrm{W}$ is lighted for $10 \text{hours}$, how much is the electrical energy consumed in $\text{joules}$.