Power is defined as the rate of doing work or work done per unit time. Note: SI unit of power is watt.

A water pump raises 50 kg of water through a height of 25 m in 5 s . Calculate the power which the pump supplies. (take g = 10 m s 2 )

Given, Mass of water lifted, m = 50 kg Height, h = 25 m Time, t = 5 s Acceleration due to gravity, g = 10 m s - 2 We know that power, P = Work done time taken P = m × g × h t P = 50 × 25 × 10 5 Power of pump, P = 2500 W

A man carrying a bag of mass 25 kg climbs up to a height of 10 m in 50 s . Calculate the power delivered by him to the bag. (take g = 10 m / s 2 )

Given, Mass of the bag, m = 25 kg Height travelled, h = 10 m Acceleration due to gravity, g = 10 m s - 2 Time taken, t = 50 s Work done against gravity, W = m g h We know that the formula to calculate power is, P = W t ∴ P = m g h t . P = 25 × 10 × 10 50 = 2500 50 = 50 W .

Pratyush can run at a speed of 8 m s against the frictional force of 10 N . His friend Adarsh can move at a speed of 3 m s against the frictional force of 25 N . Who is more powerful and why?

Given that, Pratyush is working against frictional force, F 1 = 10 N , Velocity of Pratyush, v 1 = 8 m s , Adarsh is working against frictional force, F 2 = 25 N , Velocity of Adarsh, v 2 = 3 m s , We know that, power is given by P = F × v . Therefore, power of applied by Pratyush, P 1 = F 1 × v 1 ⇒ P 1 = 10 × 8 = 80 W Also, power of applied by Adarsh, P 2 = F 2 × v 2 ⇒ P 2 = 25 × 3 = 75 W Thus, P 1 > P 2 Here, Pratyush had to use more power hence he is more powerful.

EASY

Earn 100

What is power?

Important Questions on Effect of Energy: Work, Power and Energy

HARD

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A person of 75 kg climbs up to a height of 5 m in 25 sec. Calculate the power consumed by the person. (g=10m/s²)

MEDIUM

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

Derive a relationship between SI and CGS units of work.

HARD

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A water pump lifts water from a level $10 m$ below the ground. The water is pumped at the rate of $30 kg / \min$ with negligible velocity. Calculate the minimum power the pump should have to do this work.

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

How is the unit horsepower related to the SI unit of power?

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A person of mass

100 kg

reaches a height in

10 seconds

. Find the power used by the person (

g = 10 \frac{m}{s^{2}}

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

State and define the SI unit of power.

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

1 horse power (HP)

is equal to:

MEDIUM

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A boy of mass

50 kg

runs a stair case of

45

steps in

9 \sec

. If the height of each steps is

15 cm

, find his power. (Take

g = 10 {ms}^{- 2}

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A crane

' A'

lifts a heavy load in

5 seconds

, whereas another crane

' B'

does the same work in

2 seconds

. Compare the power of crane

' A'

to that of crane

' B'

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

The power output of an engine is

3 k W

. How much work does the engine do in

20 s

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A water pump raises

50 kg

of water through a height of

25 m

5 s

. Calculate the power which the pump supplies. (take

g = 10 \frac{m}{s^{2}}

)

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

Five electric fans of

120 watts

each are used for

4 hours

. Calculate the electrical energy consumed in kilowatt-hours.

MEDIUM

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A man weighing

500 N

carried a load of

100 N

up a flight of stairs

4 m

high in

5 seconds

. What is the power?

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A man carrying a bag of mass

25 kg

climbs up to a height of

10 m

50 s

. Calculate the power delivered by him to the bag. (take

g = 10 m / s^{2}

)

MEDIUM

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

How much electrical energy in joules does a

100 watt

lamp consume in

1 minute

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

A boy of mass

50 kg

runs up a staircase of

45

steps in

9 s

. If the height of each step is

15 cm

, find his power. Take

g = 10 m s^{- 2}

MEDIUM

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

How much energy does a

100 W

electric bulb transfer in

1

minute?

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

How much energy is used for boiling water in a

2 kW

kettle for

10 minutes

? Calculate it in watt-hour.

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

Who has more power, labourer A completing a given work in

3

hours or labourer B who completes the same work in

5

hours?

EASY

Physical Science>Physics>Effect of Energy: Work, Power and Energy>Power

Pratyush can run at a speed of $8 \frac{m}{s}$ against the frictional force of $10 N$ . His friend Adarsh can move at a speed of $3 \frac{m}{s}$ against the frictional force of $25 N$ . Who is more powerful and why?

What is power?

Important Questions on Effect of Energy: Work, Power and Energy

Learn and Prepare for any exam you want !