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Practice MCQ Questions and answers on Physics-GK

Learn and practice General Knowledge questions and answers on Physics with very easy and understandable explanations. GK questions are very helpful different type of competitive exams. Page-6 section-8

Each section contains 100 MCQs on Physics .
51
A body of mass 2 kg is thrown upward with initial velocity of 20 m/s. After 2 seconds, its kinetic energy will be : (g = 10 m/s2)
Discuss
Answer & Solution
Answer: Option A
Solution:
We will use the following equation of motion to get the final velocity after 2 seconds.
V = u - gt
U = 20 m/s
g = 10
t = 2
V = 20 - 2 × 10
V = 20 - 20
V = 0
K.E = 1/2mv²
m = 2
v = 0
K.E = 0.5 × 0 × 2
= 0
52
The energy stored in a watch spring is
Discuss
Answer & Solution
Answer: Option B
Solution:
When a spring is compressed, it stores energy in form of elastic potential energy.
53
An object that has kinetic energy must be
Discuss
Answer & Solution
Answer: Option D
Solution:
In physics, we know that the kinetic energy 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. Hence, An object that has kinetic energy must be in motion i.e, moving.
54
A mass of 20 kg is at a height of 8 m above the ground. Then the potential energy possessed by the body is: [Given g = 9.8 m/s2]
Discuss
Answer & Solution
Answer: Option A
Solution:
A mass of 20 kg is at a height of 8 m above the ground. Then the potential energy possessed by the body is 1586 J.
55
A person lifts luggage of 20 kg from the ground and puts it on his head 2m above the ground. Calculate the work done by him. (g = 10 )
Discuss
Answer & Solution
Answer: Option B
Solution:
Total work done in lifting and moving the luggage is 588 Joules.
Explanation :
1. work done in lifting the luggage
= potential energy of the luggage
= mgh
where,
m = mass = 20 kg
g = acceleration due to gravity = 9.8 m/s²
h = height = 3 m
Hence,
P = mgh = 20 x 9.8 x 3
= 588 J
2. work done in moving the object,
Since now weight of the luggage is acting in downward direction and the movement is in horizontal direction, hence work done in moving the luggage is zero because component of force along horizontal direction is zero.
Total work done = 588 + 0 = 588 J.
Hence total work done in lifting and moving the luggage 588 J.
56
Work done in a free expansion process is
Discuss
Answer & Solution
Answer: Option B
Solution:
In free expansion there is no work done as there is no external external pressure. That's certainly true, in fact free expansion is an irreversible process in which a gas expands into an insulated evacuated chamber, you can think of it like ann container with a piston and the gas is left to expand in vacuum.
57
An object of 10 kg is moving with a speed of 2 m/s. The kinetic energy of the object is
Discuss
Answer & Solution
Answer: Option A
Solution:
Kinetic energy = 1/2mv2
= 1/2*10*22
= 1/2*10*4
= 5*4
= 20 J
58
If both the mass and the velocity of a body is increased to twice of their magnitude, the kinetic energy will increase by
Discuss
Answer & Solution
Answer: Option C
Solution:
If you double mass and double velocity, you get eight times the kinetic energy, no matter what your first energy is. As an object's kinetic energy increases, and momentum is mass x velocity.
59
Kinetic energy depends on
Discuss
Answer & Solution
Answer: Option D
Solution:
Kinetic energy depends on both mass and velocity of the moving body.
60
The device used to convert solar energy into electricity is
Discuss
Answer & Solution
Answer: Option A
Solution:
A photovoltaic cell, commonly called a solar cell or PV, is the technology used to convert solar energy directly into electrical power. A photovoltaic cell is a non-mechanical device usually made from silicon alloys. Sunlight is composed of photons, or particles of solar energy.