## Gravitation Questions and Answers Part-5

1. The weight of an object in the coal mine, sea level, at the top of the mountain are $W_{1}, W_{2}$  and $W_{3}$   respectively, then
a) $W_{1}<W_{2} >W_{3}$
b) $W_{1}=W_{2} =W_{3}$
c) $W_{1}<W_{2} < W_{3}$
d) $W_{1}>W_{2} >W_{3}$

Explanation: Because value of g decreases when we move either in coal mine or at the top of mountain.

2. The radii of two planets are respectively $R_{1}$ and $R_{2}$ and their densities are respectively $\rho_{1}$ and $\rho_{2}$ . The ratio of the accelerations due to gravity at their surfaces is
a) $g_{1}:g_{2}=\frac{\rho_{1}}{R_1^2}:\frac{\rho_{2}}{R_2^2}$
b) $g_{1}:g_{2}=R_{1}R_{2}:\rho_{1}\rho_{2}$
c) $g_{1}:g_{2}=R_{1}\rho_{2}:R_{2}\rho_{1}$
d) $g_{1}:g_{2}=R_{1}\rho_{1}:R_{2}\rho_{2}$

Explanation:

3. The mass of the earth is 81 times that of the moon and the radius of the earth is 3.5 times that of the moon. The ratio of the acceleration due to gravity at the surface of the moon to that at the surface of the earth is
a) 0.15
b) 0.04
c) 1
d) 6

Explanation:

4. Spot the wrong statement : The acceleration due to gravity ‘g’ decreases if
a) We go down from the surface of the earth towards its centre
b) We go up from the surface of the earth
c) We go from the equator towards the poles on the surface of the earth
d) The rotational velocity of the earth is increased

Explanation: Value of g decreases when we go from poles to equator

5.Which of the following statements is true
a) g is less at the earth's surface than at a height above it or a depth below it
b) g is same at all places on the surface of the earth
c) g has its maximum value at the equator
d) g is greater at the poles than at the equator

Explanation: g is greater at the poles than at the equator

6. A spring balance is graduated on sea level. If a body is weighed with this balance at consecutively increasing heights from earth's surface, the weight indicated by the balance
a) Will go on increasing continuously
b) Will go on decreasing continuously
c) Will remain same
d) Will first increase and then decrease

Explanation: Because value of g decreases with increasing height

7. The value of g on the earth's surface is 980 $cm\diagup sec^{2}$   . Its value at a height of 64 km from the earth's surface is
a) 960.40 $cm\diagup sec^{2}$
b) 984.90 $cm\diagup sec^{2}$
c) 982.45 $cm\diagup sec^{2}$
d) 977.55 $cm\diagup sec^{2}$

Explanation:

8. Choose the correct statement from the following : Weightlessness of an astronaut moving in a satellite is a situation of
a) Zero g
b) No gravity
c) Zero mass
d) Free fall

Explanation: Free fall

9. If the earth rotates faster than its present speed, the weight of an object will
a) Increase at the equator but remain unchanged at the poles
b) Decrease at the equator but remain unchanged at the poles
c) Remain unchanged at the equator but decrease at the poles
d) Remain unchanged at the equator but increase at the poles