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Whenever a force is applied, work is done.

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Important Questions on Work, Energy and Power

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work

A force acts on a body and displaces it by a distance

S

in a direction at an angle

θ

with the direction of force. What should be the value of

θ

to get the maximum positive work?

EASY

Physics>Mechanics>Work, Energy and Power>Work

Two persons

A

and

B

perform same amount of work in moving a body through a certain distance

d

with application of forces acting at angles

45 °

and

60 °

with the direction of displacement respectively. The ratio of force applied by person

A

to the force applied by person

B

\frac{1}{\sqrt{x}} .

The value of

x

is _________.

EASY

Physics>Mechanics>Work, Energy and Power>Work

A lawn roller has been pushed through a distance of $80 m$ by applying a force of $50 kg .$ wt in a direction inclined at $60 °$ with the ground. Calculate the work done on the roller.

EASY

Physics>Mechanics>Work, Energy and Power>Work

A small particle moves to position

5 \hat{i} - 2 \hat{j} + \hat{k}

from its initial position

2 \hat{i} + 3 \hat{j} - 4 \hat{k}

under the action of force

5 \hat{i} + 2 \hat{j} + 7 \hat{k} N

. The value of work done will be ______

J

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work

A person pushes a box on a rough horizontal platform surface. He applies a force of

200 N

over a distance of

15 m

. Thereafter, he gets progressively tired and his applied force reduces linearly with distance to

100 N

. The total distance through which the box has been moved is

30 m

. What is the work done by the person during the total movement of the box?

EASY

Physics>Mechanics>Work, Energy and Power>Work

A wire fixed at the upper end stretches by length

∆ l

by applying a force

F

. The work done in stretching is

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work

A body of mass

8 kg

, under the action of a force, is displaced according to the equation

s = \frac{t^{2}}{4} m,

where

' t'

is the time. Find the work done by the force in the first

4

seconds.

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work

The work done on a particle of mass

m

by a force

K [\frac{x}{{(x^{2} + y^{2})}^{3 / 2}} \hat{i} + \frac{y}{{(x^{2} + y^{2})}^{3 / 2}} \hat{j}]

(

K

being a constant of appropriate dimensions, when the particle is taken from the point

(a, 0)

to the point

(0, a)

along a circular path of radius

a

about the origin in the x-y plane is

EASY

Physics>Mechanics>Work, Energy and Power>Work

Two springs of spring constants

K

and

2 K

are stretched by same force. If

W_{1}

and

W_{2}

are the energies stored in them respectively then

EASY

Physics>Mechanics>Work, Energy and Power>Work

Assertion $(A)$ : The work done by the electrostatic force is zero when a point charge moves in a circular path around another charge.

Reason $(R)$ : The dot product of force and displacement vectors gives work done.

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work

Identify the correct statements from the following:

(A) Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket is negative

(B) Work done by gravitational force in lifting a bucket out of a well by a rope tied to the bucket is negative

(D) Work done by an applied force on a body moving on a rough horizontal plane with uniform velocity is zero

(E) Work done by the air resistance on an oscillating pendulum is negative

Choose the correct answer from the options given below:

HARD

Physics>Mechanics>Work, Energy and Power>Work

A force

(F) = - 5 \hat{i} - 7 \hat{j} + 3 \hat{k}

acting on a particle causes a displacement

(s) = 3 \hat{i} + 2 \hat{j} + a \hat{k}

in its own direction. If the work done is

14 J

, then the value of

a

is:

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work

A block of mass

m

is kept on a platform which starts from rest with a constant acceleration

\frac{g}{2}

upwards, as shown in the figure. Work done by normal reaction on block in time

t

is,

EASY

Physics>Mechanics>Work, Energy and Power>Work

A satellite revolves around a planet in a circular orbit. What is the work done by the satellite at any instant? Give a reason.

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work

Consider a drop of rain water having mass

1 g

falling from a height of

1 km

. It hits the ground with a speed of

50 m s^{- 1}

. Take

g

constant with a value

10 m s^{- 2}

. The work done by the (i) gravitational force and the (ii) resistive force of air is

EASY

Physics>Mechanics>Work, Energy and Power>Work

The work done to raise a mass

m

from the surface of the earth to a height

h

, which is equal to the radius of the earth is:

HARD

Physics>Mechanics>Work, Energy and Power>Work

A point particle of mass m, moves along the uniformly rough track PQR as shown in the figure. The coefficient of friction, between the particle and the rough track equals

μ

. The particle is released, from rest, from the point P and it comes to rest at a point R. The energies, lost by the ball, over the parts, PQ and QR, of the track, are equal to each other, and no energy is lost when particle changes direction from PQ to QR.
The values of the coefficient of friction