# Engineering Physics Questions and Answers – Gravitational and Gravity

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

1. Statement 1 – The length of the day is slowly increasing.
Statement 2 – The dominant effect causing a slow down in the rotation of the earth is the gravitational pull of other planets in the solar system.
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 false. The length of the day depends on the speed of rotation of the earth about its axis. As it remains constant, the length of the day is not changing. Further, the earth is not slowing down due to the gravitational pull of other planets in the solar system.

2. If the earth stops rotating, the value of g at the equator ___________
a) Increases
b) Decreases
c) No effect
d) First increases and then decreases

Explanation: At the equator, ge=g-Rω2
When ω=0, ge=g
The value of g increases if the earth stops rotating.

3. A satellite revolves very near to the earth surface. Its speed should be around?
a) 5km/s
b) 8km/s
c) 2km/s
d) 11km/s

Explanation: Near the earth’s surface,
v0=√gR=7.2km/s
Approximately 8km/s.

4. The value of escape velocity on a certain planet is 2km/s. Then the value of orbital speed for a satellite orbiting close to its surface is ___________
a) 12km/s
b) 1km/s
c) √2km/s
d) 2√2km/s

Explanation: Near earth’s surface,
v0=ve/√2=2/√2=√2 km/s.

5. If gravitational constant is decreasing with time, what will remain unchanged in case of a satellite orbiting around the earth?
a) Time period
c) Areal velocity
d) Angular velocity

Explanation: The central gravitational force decreases which does not exert any torque. Hence the angular momentum and consequently areal velocity remain unchanged.

6. An elephant and an ant are to be projected out of the earth into space. What is the velocity needed to do so?
a) Elephant needs to be projected with a higher velocity
b) Ant should be projected with a higher velocity
c) Both should be projected with the same velocity
d) Elephant cannot be projected to space

Explanation: The escape velocity ve=√2gR, does not depend upon the mass of the projected body. Thus we need the same velocity to project an elephant and an ant into space.

7. An astronaut, while revolving in a circular orbit happens to throw a spoon outside. What will happen to the spoon?
a) It will reach the earth surface
b) It will escape the universe
c) It will remain stationary
d) It will continue to move in a circular orbit

Explanation: While revolving in a circular orbit, if a spoon is thrown outside, the spoon will continue to rotate in the same circular orbit, and chase the astronaut. It will never reach the surface of the earth.

8. It is possible to place an artificial satellite in an orbit, such that it is always visible over New Delhi.
a) True
b) False

Explanation: A satellite remains always visible only if it revolves in the equatorial plane with a period of revolution equal to that of the earth. New Delhi does not lie in the region of the equatorial plane. Hence it is not possible to place an artificial satellite in an orbit such that it is always visible from New Delhi.

9. A satellite does not need ant fuel to circle around the earth.
a) True
b) False

Explanation: The gravitational force between satellite and earth provides the centripetal force required by the satellite to move in a circular orbit.

10. A satellite orbiting the earth with speed v0. To make the satellite escape, what should be the minimum percentage increase in its velocity?
a) 41.5%
b) 44.1%
c) 41.4%
d) 40%

Explanation: Required percentage increase in velocity = (ve-v0)/v0 ×100
(√2-1)×100=41.4%.

Sanfoundry Global Education & Learning Series – Engineering Physics.

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