State and define SI unit of power.

Important Questions on Work and Energy

MEDIUM

9th CBSE

IMPORTANT

Together with Science Class 9>Chapter 11 - Work and Energy>ASSESS YOURSELF>Q 35

A person carrying $10$ bricks each of mass $2.5 \mathrm{kg}$ on his head moves to a height $20 \mathrm{m}$ in $50 \mathrm{s}$. Calculate power spent in carrying bricks by the person. ($g=10 \mathrm{m} {\mathrm{s}}^{-2}$)

MEDIUM

9th CBSE

IMPORTANT

Together with Science Class 9>Chapter 11 - Work and Energy>ASSESS YOURSELF>Q 36

Two bulbs of $40 \mathrm{W}$ each are lighted for eight hours daily. Find the cost of electrical energy consumed by them in one week at $₹3$ per unit.

MEDIUM

9th CBSE

IMPORTANT

Together with Science Class 9>Chapter 11 - Work and Energy>ASSESS YOURSELF>Q 37

A man whose mass is $50 \mathrm{kg}$ moves up $15$ steps each of height $15 \mathrm{cm}$ in $45$ seconds of time. Calculate the power used in climbing those stairs. ($g=10 \mathrm{m} {\mathrm{s}}^{-2}$)

EASY

9th CBSE

IMPORTANT

Together with Science Class 9>Chapter 11 - Work and Energy>ASSESS YOURSELF>Q 38

A battery lights a bulb. Describe the energy change involved in the process.

MEDIUM

9th CBSE

IMPORTANT

Together with Science Class 9>Chapter 11 - Work and Energy>ASSESS YOURSELF>Q 38

Calculate the amount of work needed to stop a car of $500 \mathrm{kg}$, moving at a speed of $36 \mathrm{km} {\mathrm{h}}^{-1}$.