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Describe the properties of work done.

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Important Questions on Work, Energy and Power

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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 _________.

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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

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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?

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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

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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.

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Physics>Mechanics>Work, Energy and Power>Work

A time dependent force

F = 6 t

acts on a particle of mass

1 kg

. If the particle starts from the rest, the work done by the force during the first

1 \sec

will be:

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.

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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,

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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:

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Physics>Mechanics>Work, Energy and Power>Work

When a rubber-band is stretched by a distance x, it exerts a restoring force of magnitude
F = ax + bx² where a and b are constants. The work done in stretching the unstretched rubber-band by L is :

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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.

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Physics>Mechanics>Work, Energy and Power>Work

Two similar springs

P

and

Q

have spring constants

K_{P}

and

K_{Q}

, such that

K_{P} > K_{Q}

. They are stretched, first by the same amount (case a), then by the same force (case b). the work done by the springs

W_{P}

and

W_{Q}

are related as respectively, in case

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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

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A block of mass $m$ slides from rest at a height $H$ on a frictionless inclined plane as shown in the figure. It travels a distance $d$ across a rough horizontal surface with coefficient of kinetic friction $μ$ and compresses a spring of spring constant $k$ by a distance $x$ before coming to rest momentarily. Then the spring extends and the block travels back attaining a final height of $h$ .

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