Lakhmir Singh & Manjit Kaur Test: Work & Energy
20 Questions MCQ Test Physics for Class 9 | Lakhmir Singh & Manjit Kaur Test: Work & Energy
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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?
A freely falling body during its fall will have
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
A body of mass 4 kg has a momentum of 25 kg m/s, its K.E. is:
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
What happens to K.E. of a body when 3/4 th of mass is removed and its velocity is doubled?
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
Elastic potential energy of a body can be achieved by
If the velocity of a moving car is halved, its kinetic energy would
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.
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
Using the consersative law of
Energy formula
Change in potential energy =kinetic energy
M .g. h = 3500 J
35 . 10.h = 3500
h=10m
Which of the following is not an example of potential energy?
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.
How fast should a person with mass 50kg walk so that his kinetic energy is 625 J ?
K.E = 0.5mv²
v = √(2K.E / m)
= √(2 × 625 Joule / 50 kg)
= √(625 Joule / 25 kg)
= 5 m/s...
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:
Two bodies of masses m and 4 m are moving with equal kinetic energy. The ratio of velocities with which they are traveling is :
since kinetic energies are equal
KE1 = KE2
mv12/2 = 4mv22/2
v1/v2 = √4/1 = 2:1
If the speed of an object doubles, its kinetic energy becomes
If two bodies of different masses have the same K.E. then the relation between momentum and mass will be:
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.
1 J is the energy required to do ____ of work.
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.
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:
For an object to have gravitational potential energy only, it must be
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.
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.
Potential energy is energy possessed by an object due to its
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.
Which of the following produces energy because of temperature difference at various levels in ocean.
The correct option is C.
Both will have the same kinetic energy.
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