Engineering Physics Multiple Choice Questions 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
Answer: b
Clarification: 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%
Answer: c
Clarification: 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
Answer: a
Clarification: 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
Answer: c
Clarification: 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
Answer: a
Clarification: At the poles gp>ge,
Hence mgp>mge.
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
Answer: d
Clarification: 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
Answer: d
Clarification: 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