Gravitation Test

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Gravitation Test - 30

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Question 1
1 / -0

Calculate the relative density of zinc when its density is $$\displaystyle 7{ g }/{ { cm }^{ 3 } }$$.

A
$$0.7$$

B
$$3.5$$

C
$$49$$

D
$$7$$

Solution

Relative density$$(\rho_o)$$ is defined as the ratio of density of any substance to the density of water at $$\displaystyle { 4 }^{ \circ }C$$.
The relative density of water at $$\displaystyle { 4 }^{ \circ }C$$ is $$1\ g/cm^3$$.
$$\rho_o=\dfrac{Density\ of\ substance}{Density\ of\ water}$$
$$\rho_o=\dfrac{7\ g/cm^3}{1\ g/cm^3}$$
Thus the magnitude of density of any substance is equal to the magnitude of its relative density. Thus the relative density is $$7$$ and since it is the ratio of two similar quantities it has no units.
Question 2
1 / -0

Universal law of gravitation was given by:

A
Rutherford

B
Newton

C
Maxwell

D
Fleming

E
Neil Bohr

Solution

Universal law of gravitation was given by Newton.
Law states that every body in the universe attracts every other body with a force which is directly proportional to the product of their masses and inversely proportional to the square of a distance between them. The force acts along the line joining the two bodies.
Question 3
1 / -0

Archimedes principle works when the body is

A
Partially immersed in a liquid

B
Fully immersed in a liquid

C
Both A and B

D

This principle has nothing to do with the level of immersion of the body
Solution
Archimedes' Principle states that buoyant force acting on body upwards is equal in magnitude of the weight of liquid it displaces. Depending upon how much the body is immersed in liquid, and hence how much the weight of liquid is displaced, the buoyant force varies.
When the body is partially immersed, the buoyant force would be equal to only the weight of the liquid which immersed portion of the body displaced.
When the body is fully immersed, the buoyant force would be equal to the weight of the liquid which the entire body displaced on being immersed.
Question 4
1 / -0

Mass of an object on moon will be

A
One sixth of its value on earth

B
Ten times it's value on earth

C
Six times it's value on earth

D
Same as on earth

Solution

Mass is a physical quantity of an object which is independent of gravitational force. Hence, it will remain the same irrespective of the planet. However, weight is directly proportional to gravitational acceleration hence weight will be reduced to one-sixth.
Question 5
1 / -0

Weight of an object on moon will be

A
One third of it's value on earth

B
Same as on earth

C
100 times it's value on earth

D
One sixth of its value on earth

Solution

Weight of an object is directly proportional to the gravitational acceleration.

$$W=mg$$

Gravitational acceleration on moon is one sixth of earth, hence weight of an object on moon will be one sixth of its value on earth.
Question 6
1 / -0

The earth pulls all objects towards

A
its periphery

B
its centre

C
Both centre and periphery

D
Earth never pulls any objects. It is the inbuilt attractive force in a body which attracts it downwards

Solution

Any object falls down from a tree due to the gravity of earth. In fact, the earth attracts or pulls all the objects towards its centre. Every object falls vertically downwards. This direction is towards the centre of the earth. If it was not towards the centre, then the objects will fall in a direction which is not along the vertical direction.
Question 7
1 / -0

Which of the following is also called Universal law of gravitation?

A
Newton's law of gravitation

B
Archimedes' law of gravitation

C
Plank's law of gravitation

D
Bohr's law of gravitation

Solution

Newton's law of gravitation is called universal law of gravitation because it is applicable to all the bodies having mass whether the bodies are big or small or whether the bodies are terrestrial or celestial.
Newton's law of gravitation states that every particle in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particle and inversely proportional to the square of the distance between them.
$$F = \dfrac{Gm_1m_2}{r^2}$$
Question 8
1 / -0

When a solid object is immersed in a liquid, _________ force acts on the object because of the volume of liquid displaced.

A
Upward

B
Downward

C
Both $$A$$ and $$B$$

D
None of these

Solution

When an object is immersed in a liquid, the pressure at the different levels of water touching the body varies. The pressure in the water increases with increasing depth. Hence the force acting upwards due to higher pressure at the bottom is greater than the force acting downwards due to lower pressure at the top.
Hence a net upward force called buoyant force acts on the body.
Question 9
1 / -0

Magnitude of buoyant force is given by

A
Newton's first law

B

Archimedes principle

C

Newton's second law

D
None of the above

Solution

Archimedes principle, states that any body completely or partially submerged in a fluid (gas or liquid) at rest is acted upon by an upward, or buoyant force the magnitude of which is equal to the weight of the fluid displaced.
$$F_{B}=V\rho g$$
$$F_{B}\rightarrow$$buoyant force
$$V\rightarrow$$ displaced volume
$$\rho\rightarrow$$density of the liquid
$$g\rightarrow$$ acceleration due to gravity
Question 10
1 / -0

Newton said that an apple falls down from a tree because

A
Apple exerts a force of attraction on the earth

B
The earth exerts a force of attraction on the apple

C
Both are true

D
None of the options are correct

Solution

$$F= \dfrac{Gm_1 m_2}{r^2}$$
According to Isaac Newton, all objects in the universe exert an attractive force on all other objects due to their masses.
The apple falls down from a tree because the earth attracts the apple with a force which is known as gravitational force.

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Gravitation Test - 30

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Gravitation Test - 30

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SHARING IS CARING

Question 1

$$0.7$$

$$3.5$$

$$49$$

$$7$$

Solution

Question 2

Rutherford

Newton

Maxwell

Fleming

Neil Bohr

Solution

Question 3

Partially immersed in a liquid

Fully immersed in a liquid

Both A and B

This principle has nothing to do with the level of immersion of the body

Solution

Question 4

One sixth of its value on earth

Ten times it's value on earth

Six times it's value on earth

Same as on earth

Solution

Question 5

One third of it's value on earth

Same as on earth

100 times it's value on earth

One sixth of its value on earth

Solution

Question 6

its periphery

its centre

Both centre and periphery

Earth never pulls any objects. It is the inbuilt attractive force in a body which attracts it downwards

Solution

Question 7

Newton's law of gravitation

Archimedes' law of gravitation

Plank's law of gravitation

Bohr's law of gravitation

Solution

Question 8

Upward

Downward

Both $$A$$ and $$B$$

None of these

Solution

Question 9

Newton's first law

Archimedes principle

Newton's second law

None of the above

Solution

Question 10

Apple exerts a force of attraction on the earth

The earth exerts a force of attraction on the apple

Both are true

None of the options are correct

Solution

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