# Engineering Physics Questions and Answers – Intensity of Gravitational Field

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Intensity of Gravitational Field”.

1. If suddenly the gravitational force of attraction between the earth and a satellite revolving around it becomes zero, then the satellite will ___________
a) Continue to move in its orbit with the same velocity
b) Move tangentially to the original orbit with the same velocity
c) Become stationary in its orbit
d) Move towards the earth

Explanation: If the gravitational force suddenly becomes zero, the satellite will move tangentially to the original orbit with the velocity, it was revolving around the earth.

2. If the radius of the earth decreases by 1% and its mass remains the same, then the acceleration due to gravity ___________
a) Increases by 1%
b) Decreases by 1%
c) Increases by 2%
d) Decreases by 2%

Explanation: g=GM/R2
For constant G and M
∆g/g×100=2∆R/R×100=-2(-1)%=+2%
The value of g increases by 2%.

3. A gravitational law is also called ___________
a) Universal law
b) Newton’s law
c) Constant law
d) True law

Explanation: Gravitational law is also called universal law because of the fact that the law of gravitation holds good for any pair of bodies in the universe whether microscopically small or astronomically large in size.

4. If the diameter if the earth becomes twice its present value but its mass remains unchanged, then how would be the weight of an object on the surface of the earth affected?
a) 1/2 W
b) 1/3 W
c) 1/4 W
d) W

Explanation: Weight of the body,
W=mg=GMm/R2
When the diameter or radius of the earth becomes double its present value, the weight of the body will be
W’=GMm/((2R)2 )=1/4 W
That is, the weight will become one-fourth of the present value.

5. A body weighs more at the poles than at the equator.
a) True
b) False

Explanation: At the poles gp>ge,
Hence mgp>mge.
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6. At which part of the earth’s surface, the value of g is largest?
a) At the equator
b) Immediately below the equator
c) Immediately above the equator
d) At the poles

Explanation: Distance of poles from the centre of the earth is smaller than the distance of any other point on the earth’s surface from its centre. At poles, no centrifugal force acts on the body. Hence the value of g is largest at the poles.

7. A body weighed 250N on the surface. Assuming the earth to be a sphere of uniform mass density, how much would it weigh half way down to the centre of earth?
a) 240N
b) 210N
c) 195N
d) 125N

Explanation: At depth,
d=R/2
gd=g(1-d/R)=g(1-(R/2)/R)=g/2
New weight = mg/2=250/2=125N.

8. There is no atmosphere on the moon, because ___________
a) It is closer to the earth and also it has inactive inter gases in it
b) It is too far from the sun and also it has very low pressure on its outer surface
c) Escape velocity of gas molecules is greater than their root mean square velocity
d) Escape velocity of gas molecules is less than their root mean square velocity

Explanation: The required escape velocity of gas molecules is less than their root mean square velocity, therefore there is no atmosphere on the moon.

9. A missile is launched with a velocity less than escape velocity. The sum of its kinetic energy and potential energy is ___________
a) Zero
b) Positive
c) Negative
d) First positive and then negative

Explanation: For velocity less than the escape velocity, the missile is bound due to the gravitational field of the earth. Hence its total energy is negative.

10. Statement 1- The stars twinkle, while the planets do not.
Statement 2- The stars are much bigger in size than the planets.
a) Statement 1 and statement 2 are correct and statement 2 is the correct explanation of statement 1
b) Statement 1 and statement 2 are correct but statement 2 is not the correct explanation of statement 1
c) Statement 1 is true but statement 2 is false
d) Both statement 1 and 2 are false

Explanation: Both the statements are true but statement 2 is not the correct explanation of statement 1. Planets are much closer to the earth than the stars. Lights coming from planets do not show intensity variations as does the light from the stars.

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