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A motor of power $P_{0}$ is used to deliver water at a certain rate through a given horizontal pipe. To increase the rate of flow of water through the same pipe n times, the power of the motor is increased to P₁. The ratio of P₁ to P₀ is

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Important Questions on Work, Energy and Power

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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

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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):

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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

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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

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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:

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A body starts from rest, under the action of an engine working at constant power and moves along a straight line. The displacement $s$ is given as a function of time $t$ as:

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A body of mass

2 kg

is driven by an engine delivering a constant power of

1 J s^{- 1}

. the body starts from rest and moves in a straight line. After

9 s

, the body has moved a distance (in

m

)….

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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}

)

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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}

)

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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:

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A constant power delivering machine has towed a box, which was initially at rest, along a horizontal straight line. The distance moved by the box in time

t

is proportional to :-

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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})

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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:

HARD

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A car of mass

m

accelerates on a level smooth road when a constant power

p

is delivered to it. If the velocity of the car at any instant is

v,

then its velocity will be doubled after travelling a distance

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An automobile of mass

m

accelerates starting from the origin and initially at rest, while the engine supplies constant power

P

. The position is given as a function of time by:

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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:

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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})

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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 :

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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?

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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:

A motor of power P 0 is used to deliver water at a certain rate through a given horizontal pipe. To increase the rate of flow of water through the same pipe n times, the power of the motor is increased to P1. The ratio of P1 to P0 is

Important Questions on Work, Energy and Power

Learn and Prepare for any exam you want !

A motor of power $P_{0}$ is used to deliver water at a certain rate through a given horizontal pipe. To increase the rate of flow of water through the same pipe n times, the power of the motor is increased to P₁. The ratio of P₁ to P₀ is