Test: Work & Energy - 3


20 Questions MCQ Test Science Class 9 | Test: Work & Energy - 3


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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?​

Solution:
QUESTION: 2

A freely falling body during its fall will have

Solution: 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.
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

Solution: P.E. = mghtherefore m = P.E. / gh =( 2250/ (9.8× 3.4)) = (2250/33.32) kg = 67.5 kg . ANS.
QUESTION: 4

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

Solution:
QUESTION: 5

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

Solution:
QUESTION: 6

Elastic potential energy of a body can be achieved by

Solution:
QUESTION: 7

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

Solution:

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.

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

Solution:
QUESTION: 9

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

Solution:
QUESTION: 10

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

Solution:

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

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:

Solution: Change in KE is workdone by work energy theoream 60-12=48j
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 :

Solution:
QUESTION: 13

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

Solution:
QUESTION: 14

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

Solution:
QUESTION: 15

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

Solution: One joule =1newton *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.
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:

Solution: 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
QUESTION: 17

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

Solution:
QUESTION: 18

A body at rest cannot have:

Solution:
QUESTION: 19

Potential energy is energy possessed by an object due to its

Solution:
QUESTION: 20

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

Solution:

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