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Joule is the S.I unit of power.

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Important Questions on Work, Energy and Power

EASY

Physics>Mechanics>Work, Energy and Power>Power

An engine develops

20 kW

of power. How much time will it take to lift a mass of

200 kg

to a height of

40 m ? (g = 10 m s^{- 2})

EASY

Physics>Mechanics>Work, Energy and Power>Power

A body of mass

m

accelerates uniformly from rest to

v_{1}

in the time

t_{1}

. The instantaneous power delivered to the body as a function of time

EASY

Physics>Mechanics>Work, Energy and Power>Power

Water is pumped steadily out of a flooded basement, at the speed of

10 m s^{- 1}

through a hose (tube) of radius,

1 cm,

passing through a window,

3 m

above the water level. The power of the pump is (Assume

g = 10 m s^{- 2}

, density of water

= 1000 kg m^{- 3}

)

MEDIUM

Physics>Mechanics>Work, Energy and Power>Power

In each heartbeat, a heart pumps

80 m l

of blood at an average pressure of

100 mm

Hg

. Assuming

60

heartbeats per second, the power output of the heart is

(ρ_{H g} = 13.6 \times 10^{3} k g m^{- 3}) (g = 9.8 m s^{- 2})

MEDIUM

Physics>Mechanics>Work, Energy and Power>Power

A particle of mass M is moving in a circle of fixed radius R in such a way that its centripetal acceleration at time t is given by

n^{2} R t^{2}

, where

n

is a constant. The power delivered to the particle by the force acting on it, is :

MEDIUM

Physics>Mechanics>Work, Energy and Power>Power

Water is falling on the blades of a turbine from a height of

25 m . 3 \times 10^{3} kg

of water pours on the blade per minute. If the whole of energy is transferred to the turbine, power delivered is:

EASY

Physics>Mechanics>Work, Energy and Power>Power

A body at rest is moved along a horizontal straight line by a machine delivering a constant power. The distance moved by the body in time $t$ is proportional to:

EASY

Physics>Mechanics>Work, Energy and Power>Power

A water pump rated

600 W,

has an efficiency of

95 % .

If it is used to raise water through vertical distance of

60 m .

The volume of water drawn in

20

minutes, is [Use density of water

= 1000 kg m^{- 3}, g = 10 m / s^{2}

]

MEDIUM

Physics>Mechanics>Work, Energy and Power>Power

A particle is moving unidirectional on a horizontal plane under the action of a constant power supplying energy source. The displacement (s) – time (t) graph that describes the motion of the particle is (graphs are drawn schematically and are not to scale):

EASY

Physics>Mechanics>Work, Energy and Power>Power

A body is initially at rest. It undergoes one dimensional motion with constant acceleration. The power delivered to it at time

t

is proportional to

EASY

Physics>Mechanics>Work, Energy and Power>Power

The heart of a man pumps

5

litres of blood through the arteries per minute at a pressure of

150 mm

of mercury. If the density of mercury be

13.6 \times 10^{3} k g m^{- 3}

and

g = 10 m s^{- 2}

, then the power of heart in watt is:

EASY

Physics>Mechanics>Work, Energy and Power>Power

Water falls down a

500.0 m

shaft to reach a turbine which generates electricity. How much water must fall per second in order to generate

1.00 \times 10^{9}

watts of power ? (Assume

50 %

efficiency of conversion and

g = 10 m s^{- 1}

)

EASY

Physics>Mechanics>Work, Energy and Power>Power

A machine gun fires

360

bullets per minute. Each bullet travels with velocity of

500 m s^{- 1}

. If the power of the machine gun is

4.5 kW

then the mass of each bullet is:

MEDIUM

Physics>Mechanics>Work, Energy and Power>Power

A particle of mass

m

is driven by a machine that delivers a constant power

k

watts. If the particle starts from rest the force on the particle at time

t

is:

EASY

Physics>Mechanics>Work, Energy and Power>Power

If the engine of a train of mass

2.05 \times 10^{6} kg

requires a duration of

7

minutes for changing its velocity from

5 m \cdot s^{- 1}

25 m \cdot s^{- 1},

find the power of the engine.

HARD

Physics>Mechanics>Work, Energy and Power>Power

A constant force of

5 N

accelerates a stationary particle of mass

500 gm

through a displacement of

5 m .

The average power delivered is

EASY

Physics>Mechanics>Work, Energy and Power>Power

A quarter horse power motor runs at a speed of

600 rpm .

Assuming

60 %

efficiency, the work done by the motor in one rotation is

MEDIUM

Physics>Mechanics>Work, Energy and Power>Power

A body is moved along a straight line by a machine delivering constant power. The distance moved by the body in time '

t

' is proportional to

MEDIUM

Physics>Mechanics>Work, Energy and Power>Power

A car of weight W is on an inclined road that rises by 100 m over a distance of 1km and applies a constant frictional force

\frac{W}{20}

on the car. While moving uphill on the road at a speed of

10 m s^{- 1}

, the car needs power P. If it needs power

\frac{P}{2}

while moving downhill at speed

υ

then value of

υ

is:

EASY

Physics>Mechanics>Work, Energy and Power>Power

A body of mass

1 kg

begins to move from rest under the action of a time dependent force

\vec{F} = (2 t \hat{i} + 3 t^{2} \hat{j}) N

, where

\hat{i}

and

\hat{j}

are unit vectors along x and y axis. What power will be developed by the force at the time t?

Joule is the S.I unit of power.

Important Questions on Work, Energy and Power

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