MEDIUM

Earn 100

Assertion: When a spring is elongated work done by spring is negative but when it compressed work done by spring is positive.

Reason: Work done by spring is path independent.

50% studentsanswered this correctly

Important Questions on Work, Energy and Power

HARD

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

A particle is moved along a path

A B - B C - C D - D E - E F - F A,

as shown in figure, in presence of a force

\vec{F} = (α y \hat{i} + 2 α x \hat{j}) N,

where

x

and

y

are in meter and

α = - 1 N m^{- 1} .

The work done on the particle by this force

\vec{F}

will be ____ Joule.
Question Image

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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

HARD

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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

μ

and the distance

x = (Q R)

, are respectively close to:

Question Image

HARD

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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 Done by a Force

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

EASY

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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:

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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 Done by a Force

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 Done by a Force

A particle moves from a point

(- 2 \hat{i} + 5 \hat{j})

(4 \hat{j} + 3 \hat{k})

when a force of

(4 \hat{i} + 3 \hat{j}) N

is applied. How much work has been done by the force?

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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:

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

Consider a force

\vec{F} = - x \hat{i} + y \hat{j}

. The work done by this force in moving a particle from point

A (1,0)

B (0,1)

along the line segment is : (all quantities are in SI units)

Question Image

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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,

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

If a force

\vec{F} = \hat{i} - 2 \hat{j} - 4 \hat{k}

acting on a particle displaces it from

(1, 1, 1)

(2, - 1, 0),

then the work done by the force (in units of work) is

EASY

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

A force

F = 20 + 10 y

acts on a particle in

y

-direction where

F

is in Newton and

y

is in meter. Work done by this force to move the particle from

y = 0

y = 1 m

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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 Done by a Force

A particle of mass

10 g

is thrown vertically upwards with a speed of

20 m s^{- 1}

. The work done by the gravitational force during the time the particle moves upward is

EASY

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

When a rubber string is stretched through a distance

x

, the restoring force developed has a magnitude

(p x + q x^{2} + r x^{3})

where

p, q

and

r

are constants. Work done in stretching the unstretched rubber string by a distance

l

, is

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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 $h$ .

Question Image

Then

MEDIUM

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

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 :

HARD

Physics>Mechanics>Work, Energy and Power>Work Done by a Force

A block of mass

m,

lying on a smooth horizontal surface, is attached to a spring (of negligible mass) of spring constant

k .

The other end of the spring is fixed, as shown in the figure. The block is initially at rest in its equilibrium position. If now the block is pulled with a constant force

F,

the maximum speed of the block is:
Question Image

Assertion: When a spring is elongated work done by spring is negative but when it compressed work done by spring is positive. Reason: Work done by spring is path independent.

Important Questions on Work, Energy and Power

Learn and Prepare for any exam you want !

Assertion: When a spring is elongated work done by spring is negative but when it compressed work done by spring is positive.

Reason: Work done by spring is path independent.