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Lakhmir Singh & Manjit Kaur Test: Work & Energy


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20 Questions MCQ Test Physics for Class 9 | Lakhmir Singh & Manjit Kaur Test: Work & Energy

Lakhmir Singh & Manjit Kaur Test: Work & Energy for Class 9 2022 is part of Physics for Class 9 preparation. The Lakhmir Singh & Manjit Kaur Test: Work & Energy questions and answers have been prepared according to the Class 9 exam syllabus.The Lakhmir Singh & Manjit Kaur Test: Work & Energy MCQs are made for Class 9 2022 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Lakhmir Singh & Manjit Kaur Test: Work & Energy below.
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Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 1

A body is acted upon by a force 25 N acquires of 2.5 ms-2 and covers a distance of the force. If the body starts from rest, the Kinetic energy acquired by it is?​

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 2

A freely falling body during its fall will have

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 2 Object Falling from Rest. As an object falls from rest, its gravitational potential energy is converted to kinetic energy. Conservation of energy as a tool permits the calculation of the velocity just before it hits the surface. K.E. = J, which is of course equal to its initial potential energy.
Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 3

A boy climbs on to a wall that is 3.4 m high and gains 2250 J of potential energy. What is the mass of the boy? Take g = 9.8 m/Sec2

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 3 P.E. = mghtherefore m = P.E. / gh =( 2250/ (9.8× 3.4)) = (2250/33.32) kg = 67.5 kg . ANS.
Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 4

A body of mass 4 kg has a momentum of 25 kg m/s, its K.E. is:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 4

The correct answer is B asMomentum = mass × velocity
4 = 25 × v
V = 4/25
V = 6.25

To find the kinetic energy ,
KE = 1/2 m v^2
= 1/2 × 25 ×6.25x6.25
= 78.12 J
 

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 5

What happens to K.E. of a body when 3/4 th of mass is removed and its velocity is doubled?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 5

The correct answer is B as
 let the mass=m
then, m-3/4m=m/4
and velocity=2v
kinetic energy=1/2×mv2
=1/2×m/4×(2v2)
=1/2×m/4×4v2
=1/2mv2

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 6

Elastic potential energy of a body can be achieved by

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 7

If the velocity of a moving car is halved, its kinetic energy would

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 7

Kinetic Energy = (1/2) mv2.

If the velocity of a body is halved, its kinetic energy becomes one fourth as kinetic energy is directly proportional to velocity squared.

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 8

A fish with weight 35 kg dives and hits the ground (zero height) with kinetic energy equal to 3500J. Find the height through which fish dived. Take g = 10 m/s2

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 8

Using the consersative law of 
Energy formula
Change in potential energy =kinetic energy
 M .g. h = 3500 J
35 . 10.h = 3500
h=10m

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 9

Which of the following is not an example of potential energy?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 9

The correct option is D.
A moving car is an example of kinetic energy whereas water stored in a dam, compressed spring and stretched rubber band are examples of potential energy.

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 10

How fast should a person with mass 50kg walk so that his kinetic energy is 625 J ?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 10

K.E = 0.5mv²
v = √(2K.E / m)
= √(2 × 625 Joule / 50 kg)
= √(625 Joule / 25 kg)
= 5 m/s...

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 11

The kinetic energy of a body changes from 12 J to 60 J due to the action of a force of 5N on an object of mass 4 kg. The work done by the force is:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 11 Change in KE is workdone by work energy theoream 60-12=48j
Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 12

Two bodies of masses m and 4 m are moving with equal kinetic energy. The ratio of velocities with which they are traveling is :

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 12

since kinetic energies are equal

KE1 = KE2

mv12/2 = 4mv22/2

v1/v2 = √4/1 = 2:1

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 13

If the speed of an object doubles, its kinetic energy becomes

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 14

If two bodies of different masses have the same K.E. then the relation between momentum and mass will be:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 14

KE = K = 1 /2( mv2
We know, p = mv
⇒ K = p2 / 2m
 p2  =  2Km
As, KE is Same, ie . Constant, momentum would be directly proportional to the square root of mass.

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 15

1 J is the energy required to do ____ of work.

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 15

One joule =1 newton x 1 meter

since one joule refers to the energy transferred to an object when a force of one newton acts on a body in the direction of motion through a distance of one meter.

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 16

A body of mass 44 kg is moving at a velocity of 10 m/s is brought to rest in 10mins, the work done is:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 16 Mass (m)- 44 kg initial velocity (u) - 10m/s final velocity (v) - 0 time (t)- 10min =600s At first, acceleration (a) = v-u/t =0-10/600 = -1/60m per sec square using 2nd equation of motion s = ut +1/2at^2 s = 10*600 + 1/2*(-1/60*600*600) s=3000m Now, 2nd law of motion Force = ma = 44*(-1/60)=-11/15 N finally, work done=F*s=-11/15*3000= -22000J
Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 17

For an object to have gravitational potential energy only, it must be

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 17

The correct option is D.
An object possesses gravitational potential energy if it is positioned at a height above (or below) the zero height. An object possesses elastic potential energy if it is at a position on an elastic medium other than the equilibrium position.

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 18

A body at rest cannot have:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 18

In physics the Kinetic energy (KE) of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. 

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 19

Potential energy is energy possessed by an object due to its

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 19

The correct option is Option C.
Potential energy is the energy that is stored in an object due to its position relative to some zero position. An object possesses gravitational potential energy if it is positioned at a height above (or below) the zero height.

Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 20

Which of the following produces energy because of temperature difference at various levels in ocean.      

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Work & Energy - Question 20

The correct option is C.
 Both will have the same kinetic energy.
 

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