Unit – 6 : Gravitation (Multiple Choice Questions)

1. The linear momentum and position vector of a planet are perpendicular to each other at

a) perihelion and aphelion
b) at all points
c) only at perihelion
d) no point
Answer: a)

2. If the masses of the Earth and Sun suddenly double, the gravitational force between them will

a) remain the same
b) increase 2 times
c) increase 4 times
d) decrease 2 times
Answer: c)

3. A planet moving along an elliptical orbit is closest to the Sun at distance $r_1$ and farthest at $r_2$. If $v_1$ and $v_2$ are linear speeds respectively, then the ratio $\dfrac{v_1}{v_2}$ is

a) $\dfrac{r_2}{r_1}$
b) $\left(\dfrac{r_2}{r_1}\right)^2$
c) $\dfrac{r_1}{r_2}$
d) $\left(\dfrac{r_1}{r_2}\right)^2$
Answer: a)

4. The time period of a satellite orbiting Earth in a circular orbit is independent of

a) radius of the orbit
b) mass of the satellite
c) both mass and radius
d) neither mass nor radius
Answer: b)

5. If the distance between the Earth and Sun were doubled, the number of days in a year would be

a) 64.5
b) 1032
c) 182.5
d) 730
Answer: b)

6. According to Kepler’s second law, equal areas are swept in equal intervals of time. This law is a consequence of

a) conservation of linear momentum
b) conservation of angular momentum
c) conservation of energy
d) conservation of kinetic energy
Answer: b)

7. The gravitational potential energy of the Moon with respect to Earth is

a) always positive
b) always negative
c) can be positive or negative
d) always zero
Answer: b)

8. The kinetic energies of a planet at positions A, B and C in an elliptical orbit are $K_A, K_B$ and $K_C$ respectively.

Elliptical orbit showing positions A, B, C and Sun S
a) $K_A > K_B > K_C$
b) $K_B < K_A < K_C$
c) $K_A < K_B < K_C$
d) $K_B > K_A > K_C$
Answer: a)

9. The work done by the Sun’s gravitational force on the Earth is

a) always zero
b) always positive
c) can be positive or negative
d) always negative
Answer: c)

10. If the mass and radius of the Earth are both doubled, the acceleration due to gravity $g$ will

a) remain same
b) $\dfrac{g}{2}$
c) $2g$
d) $4g$
Answer: b)

11. The magnitude of the Sun’s gravitational field as experienced by Earth

a) remains same throughout the year
b) decreases in January and increases in July
c) decreases in July and increases in January
d) increases during day and decreases during night
Answer: c)

12. If a person moves from Chennai to Trichy, his weight

a) increases
b) decreases
c) remains same
d) increases and then decreases
Answer: b)

13. An object of mass 10 kg is hanging on a spring scale in a lift. If the lift is in free fall, the reading of the spring scale is

a) 98 N
b) zero
c) 49 N
d) 9.8 N
Answer: b)

14. If the acceleration due to gravity becomes 4 times its original value, the escape speed will

a) remain same
b) 2 times original value
c) becomes halved
d) 4 times original value
Answer: b)

15. The kinetic energy of a satellite orbiting around the Earth is

a) equal to potential energy
b) less than potential energy
c) greater than kinetic energy
d) zero
Answer: b)