A particle of mass m is initially at rest at the origin. It is subjected to a force and starts moving along the x - axis. Its kinetic energy changes with time as d K d t = γ t , where γ is a positive constant of appropriate dimensions. Which of the following statements is (are) true?

The distance of the particle from the origin increases linearly with time

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A child is swinging a swing. Minimum and maximum heights of swing from earth’s surface are 0.75 m and 2 m respectively. The maximum velocity of this swing is:

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Important Questions on Work, Energy and Power

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

Which of the following interactions is the weakest?

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

The ratio

(\frac{E}{W})

of relative strength of electromagnetic force

(E)

to weak nuclear force

(W)

is,

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

(A) Ratio of the relative strength of gravitational to weak force is nearly $10^{- 3}$
(B) Ratio of the relative strength of gravitational to weak force is less than $10^{- 3}$
(C) Ratio of the relative strength of strong nuclear to electromagnetic force is nearly $10^{2}$
(D) Ratio of the relative strength of strong nuclear to electromagnetic force is nearly $10^{- 2}$ .

Which of the following is true?

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

The potential energy of a system increases if work is done

MEDIUM

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A shell of mass

20 g

is fired by a gun of mass

100 kg .

If the shell leaves the gun with a speed of

800 m / s,

the speed of recoil of the gun is

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

Two bodies

A

and

B

having masses in the ratio of

3 : 1

possesses the same kinetic energy. The ratio of linear momentum of

B

A

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

Match the columns I and II

	Column I		Column II
A	Stoke's law	I	Pressure and energy
B	Turbulence	II	Hydraulic lift
C	Bernoulli's Principle	III	Viscous drag
D	Pascal's law	IV	Reynold's number

The correct match is

HARD

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A particle is moving in a circle of radius

r

under the action of a force

F = α r^{2}

which is directed towards centre of the circle. Total mechanical energy (kinetic energy + potential energy) of the particle is (take potential energy

= 0

for

r = 0

HARD

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

The maximum and minimum distances of a comet from the sun are

1.4 \times 10^{12} m

and

7 \times 10^{10}

m .

If it's velocity nearest to the sun is

6 \times 10^{14} m / s,

what is its velocity in the farthest position? (Assume the comet to be spherical)

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

Which of the following statement is incorrect?

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A particle which is experiencing a force, given by

\vec{F} = 3 \hat{i} - 12 \hat{j}

, undergoes a displacement of

\vec{d} = 4 \hat{i}

. If the particle had a kinetic energy of

3 J

at the beginning of the displacement, what is its kinetic energy at the end of the displacement?

HARD

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

In a particle accelerator, a current of

500 μ A

is carried by a proton beam in which each proton has a speed of

3 \times 10^{7} m / s

. The cross-sectional area of the beam is

1.50 m m^{2} .

The charge density in this beam (in

C / m^{3})

is close to

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A force acts on a

2 kg

object so that its position is given as a function of time as

x = 3 t^{2} + 5 .

What is the work done by this force in first

5

seconds?

MEDIUM

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A running man has half the kinetic energy of that of a boy of half of his mass. The man speeds up by

1 m s^{- 1}

to have the same kinetic energy as that of the boy. The original speed of the man will be

HARD

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A particle of mass

m

is initially at rest at the origin. It is subjected to a force and starts moving along the x - axis. Its kinetic energy changes with time as

\frac{d K}{d t} = γ t,

where

γ

is a positive constant of appropriate dimensions. Which of the following statements is (are) true?

MEDIUM

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A body of mass

m

starts moving from rest along

x -

axis so that its velocity varies as

v = a \sqrt{s}

where

a

is a constant and

s

is the distance covered by the body. The total work done by all the forces acting on the body in the first

t

second after the start of the motion is

MEDIUM

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A block of mass

10 kg

, moving in

x

direction with a constant speed of

10 m s^{- 1}

, is subjected to a retarding force

F = [(0 .1) x] J m^{- 1}

during its travel from

x = 20 m

30 m

. Its final kinetic energy will be:

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

Which of the following is a possible final step in applying the scientific method?

HARD

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

A train is moving slowly at

2 m / s

next to a railway platform. A man,

1.5 m

tall, alights from the train such that his feet are fixed on the ground. Taking him to be a rigid body, the instantaneous angular velocity (in

rad / s

) is

EASY

Physics>Mechanics>Work, Energy and Power>Kinetic and Potential Energy

Let

G, W, S

and

E

be relative strengths of gravitational, weak nuclear, strong nuclear and electromagnetic forces. Identify the correct option

A child is swinging a swing. Minimum and maximum heights of swing from earth’s surface are 0.75 m and 2 m respectively. The maximum velocity of this swing is:

Important Questions on Work, Energy and Power

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