Mechanics (Physics) (Part-3)

Total Questions: 50

41. What is the value of g? (g stands for acceleration due to gravitational force of the earth) [S.S.C. Online CHSL (T-I) 17.03.2020 (Shift-II)]

Correct Answer: (c) 9.8 m/s²
Solution:The acceleration due to the gravitational force of the earth is called acceleration due to gravity.

Its value for Earth is 9.8 m/s².
It is represented by "g" ie. g= 9.8 m/s²

42. Weight (W) of a body can be given by the formula: [S.S.C. Online CHSL (T-I) 24.01.2017 (Shift-III)]

Correct Answer: (d) W = mg
Solution:The weight (W) of a body can be given by the formula:
W = m × g
Where:

W = weight of the body (in newtons, N)
m = mass of the body (in kilograms, kg)
g = acceleration due to gravity (in m/s²)
⇒ on Earth, approximately 9.8 m/s².
So, weight is the force with which gravity pulls a body toward the center of a planet.

43. Who among the following was the first to conclude that in a vacuum, all objects fall with the same acceleration g and reach the ground at the same time? [S.S.C. Online CGL (T-I) 17.08.2021 (Shift-III)]

Correct Answer: (c) Galileo Galilei
Solution:Galileo was the first to scientifically conclude that in the absence of air resistance (i.e., in a vacuum), all objects fall at the same rate, regardless of their mass.

Galileo demonstrated through experiments (like rolling balls down inclined planes) and theoretical reasoning that:

The acceleration due to gravity (g) is constant for all objects in free fall.
Therefore, in a vacuum, all objects fall with the same acceleration and will hit the ground at the same time if dropped from the same height.

44. The rate of change of impulse of an object is proportional to the force exerted on it, according to which Newton's principle? [C.P.O. S.I. 4.06.2016 (Shift-I)]

Correct Answer: (c) Newton's second law of motion
Solution:

"The rate of change of impulse of an object is proportional to the force exerted on it based on Newton’s Second Law of Motion."
Newton’s Second Law states:
Force (F) is equal to the rate of change of momentum (or impulse) with respect to time.
Mathematically:
F = dp/dt,
where
p = momentum = mass × velocity
And since impulse = change in momentum, this law also ties force directly to impulse.

45. When an object is transferred from earth to the moon, then _____ . [S.S.C. Online Stenographer 14.09.2017 (Shift-I)]

Correct Answer: (d) its mass remains unchanged
Solution:When an object is transferred from Earth to the Moon, then its weight decreases, but its mass remains the same.

Mass is the amount of matter in an object — it does not change with location.
Weight depends on gravity, and the Moon’s gravity is about 1/6th that of Earth.
⇒ So, on the Moon, the object weighs less, but it still has the same mass.

46. If speed of rotation of the earth increases, the weight of the body_______. [S.S.C. Online Graduation Level (T-I) 11.09.2016 (Shift-III)]

Correct Answer: (a) decreases
Solution:If the speed of rotation of the Earth increases, the weight of a body decreases.
If the speed of rotation of the Earth increases, the weight of the body decreases.
Explanation:

Weight is the force with which the Earth pulls an object toward its center, calculated as:
Weight=mass×effective gravity
When the Earth rotates faster, the centrifugal force acting on objects (especially at the equator) increases.
This centrifugal force acts outward, opposing the pull of gravity.
As a result, the net (effective) gravitational force decreases, making the object weigh less.

47. A body in equilibrium_______. [S.S.C. Online CHSL (T-I) 21.01.2017 (Shift-I)]

Correct Answer: (e) (b and c)
Solution:A body in equilibrium is either at rest or moving with constant velocity in a straight line.
A body in equilibrium experiences zero net force and zero net torque.
This can happen in two cases:

Static equilibrium – the body is at rest.
Dynamic equilibrium – the body is moving at constant velocity (no acceleration).

48. The strain produced in a body is directly proportional to the stress applied which is called ______. [S.S.C. Online CHSL (T-I) 15.01.2017 (Shift-I)]

Correct Answer: (b) Hooke's Law
Solution:According to Hooke's law, the extent of change in the shape and size of an elastic material due to stress on an object is directly proportional to the amount of stress exerted on it.

49. Why does the Earth have its atmosphere? [S.S.C. Online Graduation Level (T-I) 27.08.2016 (Shift-III)]

Correct Answer: (c) Gravity
Solution:The Earth has its atmosphere because its gravity holds gases around it, and other factors like its magnetic field, temperature, and geological activity help sustain it.

50. What is the height of a geostationary satellite approximately (in km) above the surface of the earth? [S.S.C. Online C.P.O.S.I. (T-I) 1.07.2017 (Shift-II)]

Correct Answer: (a) 36000
Solution:

The height of a geostationary satellite above the surface of the Earth is approximately:
35,786 kilometers (km)
Explanation:

A geostationary satellite orbits the Earth once every 24 hours, matching the Earth’s rotation.

It remains fixed over a single point on the equator.
To achieve this, it must be placed at a precise altitude where the gravitational force and the centripetal force due to orbital motion balance out.

This altitude from Earth's center is about 42,164 km.
Since Earth’s radius is about 6,378 km, the height above the surface is:
42,164 km−6,378 km≈35,786 km=36000km
This is the standard altitude for geostationary satellites.