Gravitation Test

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Gravitation Test - 5

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Weekly Quiz Competition

Question 1
1 / -0

SI unit of gravitational constant is __________.

A
N m²kg²

B
N m²kg^-²

C
N m²s^-²

D
N m kg^-²

Solution

We know that:
Thus we get, [G] = [F.R² / m² ] = [F] x L² x M^-2= [F] M^-2 L²= N kg^-2 m²
Question 2
1 / -0

The dimensions of gravitational constant G is:

A
[L] [M] [T]

B
[L]³[M] [T]²

C
[L]³[M]^-1[T]^-²

D
[L]³[T]^-²

Solution

From Newton’s law of gravitation,
Since, Force (F) = Mass × Acceleration = M × [LT^-2]
∴ The dimensional formula of force = M¹ L¹ T^-2
⇒ Gravitational Constant (G) = F × r² × [m₁m₂]^-1
Or, G = [M¹ L¹ T^-2] × [L]² × [M]^-2 = [M^-1 L³ T^-2].
Therefore, the gravitational constant is dimensionally represented as [L]³[M]^-1[T]^-².
Question 3
1 / -0

The tides are formed due to:

A
Force of attraction between moon and ocean water.

B
Force of attraction between earth and ocean water and movement of wind.

C
Movement of Wind.

D
Force of attraction between earth and ocean water.

Solution

Tides refer to the rise and fall of our oceans' surfaces. It is caused by the attractive forces of the Moon and Sun's gravitational fields as well as the centrifugal force due to the Earth's spin.
Question 4
1 / -0

Two bodies with same mass “m” separated by a distance “r” exert a gravitational force of F on each other. Suppose the distance between them is doubled and the force becomes F’. The ratio of two forces is

A
1:4

B
4:1

C
1:2

D
2:1

Solution

We know that the force of gravitation is inversely proportional to square of the distance between the two bodies,
i.e. F∝ r^-2
Hence, when the distance between them will be doubled, the force will be reduced by 4 times
So, the ratio will be 4:1
Question 5
1 / -0

The mass of the body on moon is 40kg, what is the weight on the earth.

A
240kg

B
392N

C
240N

D
400kg

Solution

Weight = Mass * Accelertion due to gravity = 40 * 9.8 = 392 N
Question 6
1 / -0

What is the value of G in cgs system of units?

A

B

C

D

Solution

The value of G is universally constant = 6.67 × 10^-8 dyne.cm²/g²
We know:
1 dyne = 10^-5 N
1 cm = 10^-2 m
1 g = 10^-3 kg
⇒ 6.67 × 10^-8 × ( 10^-5) .(10^-2)²/(10^-3)² Nm²/kg² = 6.67 × 10^-8 { 10^-5× 10^-4 /10^-6} Nm²/kg²
= 6.67 × 10^-8 × 10^-3 N.m²/kg²= 6.67× 10^-11 Nm²/kg²
Question 7
1 / -0

Gravitation follows:

A
Newton’s Third Law of Motion

B
Gravitation follows none of the principles or laws.

C
Principle of Superposition

D
Principle of Superposition and Newton’s Third Law of Motion
Solution
Gravitational force strictly follows Newton’s Third Law of motion i.e. for every action force there is an equal and opposite reaction force.
Gravitational forces add up like vectors i.e. they obey the principle of superposition.
Question 8
1 / -0

G is a universal gravitational constant, its value is:

A
6.672 x 10¹¹ N.kg²/m²

B
6.672 x 10^-11N.kg²/m²

C
6.672 x 10^-11N.m²/kg²

D
6.672 x 10¹¹ N.m²/kg²

Solution

We know that: [g] = [G.m.m / r.r]
Since the unit of G must be same as the unit of g.r.r / m.m i.e. Nm² /kg²
Also, we know that G is very very less than 1 as the gravitational force is a very weak force.
Question 9
1 / -0

In orbit, objects inside a spacecraft feel weightless:

A
as mass of objects becomes zero.

B
as acceleration due to gravity is zero in space.

C
as objects inside are in free fall because they have the same acceleration as outside the spacecraft.

D
as acceleration due to gravity is less in spacecraft.
Solution
Astronauts float around in space because there is no gravity in space.
Astronauts are so far from the Earth that gravity is so small. This is why NASA calls it microgravity.
Question 10
1 / -0

What pulls a ball back to earth?

A
Gas

B
Gravity

C
Friction

D
Molecules

Solution

The gravitational force of the earth acts on every object having mass. When a ball is thrown upwards the gravitational force of the earth acts against the velocity of the object and pulls the ball downwards, i.e, towards itself.
Thus, gravity pulls a ball back to earth.

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Gravitation Test - 5

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Gravitation Test - 5

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Question 1

N m2 kg2

N m2 kg-2

N m2 s-2

N m kg-2

Solution

Question 2

[L] [M] [T]

[L]3 [M] [T]2

[L]3 [M]-1 [T]-2

[L]3 [T]-2

Solution

Question 3

Force of attraction between moon and ocean water.

Force of attraction between earth and ocean water and movement of wind.

Movement of Wind.

Force of attraction between earth and ocean water.

Solution

Question 4

1:4

4:1

1:2

2:1

Solution

Question 5

240kg

392N

240N

400kg

Solution

Question 6

Solution

Question 7

Newton’s Third Law of Motion

Gravitation follows none of the principles or laws.

Principle of Superposition

Principle of Superposition and Newton’s Third Law of Motion

Solution

Question 8

6.672 x 1011 N.kg2/m2

6.672 x 10-11 N.kg2/m2

6.672 x 10-11 N.m2/kg2

6.672 x 1011 N.m2/kg2

Solution

Question 9

as mass of objects becomes zero.

as acceleration due to gravity is zero in space.

as objects inside are in free fall because they have the same acceleration as outside the spacecraft.

as acceleration due to gravity is less in spacecraft.

Solution

Question 10

Gas

Gravity

Friction

Molecules

Solution

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N m²kg²

N m²kg^-²

N m²s^-²

N m kg^-²

[L]³[M] [T]²

[L]³[M]^-1[T]^-²

[L]³[T]^-²

6.672 x 10¹¹ N.kg²/m²

6.672 x 10^-11N.kg²/m²

6.672 x 10^-11N.m²/kg²

6.672 x 10¹¹ N.m²/kg²