# Class 9 Science Important Questions for Gravitation

Given below are the Gravitation Class 9 Worksheet
(a) Very Short questions
(b) Short questions
(c) Moderate Question type
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## Very Short Answer type Questions

Question 1
State the significance of universal law of gravitation.
Question 2
The value of gravitational constant G on earth is $6.67 \times 10^{-11} \ Nm^2/kg^2$. What is its value on the surface of moon?
Question 3
Two objects of masses $m_1$ and $m_2$ are dropped in vacuum from a height above the surface of earth (m1 is greater than m2). Which one will reach the ground first and why?
Question 4
Suppose gravity of earth suddenly becomes zero, then which direction will the moon begin to move if no other celestial body affects it?
Question 5
State the name and type of force which is responsible for holding the solar system together.
Question 6
The factors associated with the motion of an object are: Force, Velocity, Acceleration and Momentum. Out of these four factors which one remains constant for all bodies – large or small undergoing a free fall?
Question 7
Which force is responsible for acceleration of a body in free fall?
Question 8
What will be the acceleration of free fall?
Question 9
A cricket ball thrown vertically upwards, reaches a maximum height of 5 metres. Find the initial speed of the ball. ($g = 9.8 \ m/s^2$)
Question 10
What will be the mass of a body at the centre of the earth as compared to other places on the earth?
Question 11
If the weight of a body on the earth is 6 N, what will it be on the moon? (Given that acceleration due to gravity on moon is one – sixth of that on the earth.)
Question 12
State universal law of gravitation. How the force between the two bodies is affected if the distance between them is tripled?

Question 13
“Several phenomena of celestial bodies were believed to be unconnected but universal law of gravitation was successful to explain them”. Mention any two phenomena.
Question 14
A stone and the earth attract each other with an equal and opposite force. Why then we see only the stone falling towards the earth but not the earth rising towards the stone?
Question 15
Give reasons:
(a) Moon does not have atmosphere
. (b) If you jump on the moon, you will rise much higher than if you jump on the earth.
Question 16
Give reasons
(a) As the altitude increases, how do the weight and mass of the body vary?
(b) A stone resting on the ground has a gravitational force of 20 N acting on it. What is the weight and mass of the stone? (Take $g = 10 \ ms^{-2}$)
Question 17
Your mass on earth is 50 kg. Planet m has two times force of gravity of that on earth. What will be your mass and weight on planet m?
Question 18
What is the source of centripetal force that a planet requires to revolve around the sun? on what factors does that force depend?
Question 19
All the planets are moving in circular orbits. What provides the necessary force for this motion and what is the direction of this force? Write the name of this force. What will happen if this force disappears suddenly?
Question 20
What happens to the gravitational force between two objects if the mass of one object is tripled? Explain with the help of formula.
Question 21
The mass of sun is $2 \times\ {10}^{30}$ kg and the mass of earth is $6 \times\ {10}^{24}$ kg. if the average distance between the sun and the earth be $1.5 \times\ {10}^8$ km calculate the force of gravitation between them. (Take G = $6.7 \times\ {10}^{-11}\ {Nm}^2/{kg}^2$)
Question 22
An object is thrown vertically upwards and rises to a height of 10 m. calculate the velocity with which the object was thrown upwards.
Question 23
A stone thrown vertically upwards reaches the maximum height in 3 m. if the acceleration of the stone be $10 \ m/s^2$, calculate its initial velocity.
Question 25
A stone resting on the ground has a gravitational force of 20 N acting on it. What is the weight of the stone? Find its mass. ($g = 10 \ ms^{-2}$)
Question 26
It is said that the mass of an object remains constant at all places while weight may change. Why?
Question 27
How does weight of an object change on moving from equator to poles? When can the weight of an object be zero?
Question 28
Your mass on earth is 50 kg. Planet 'M' has two times force of gravity on earth. What will be your mass and weight on planet 'M'? ($g = 10 \ ms^{-2}$)
Question 30
A man’s weight when taken at the poles is 600 N. will his weight remain the same when measured at the equator? Will there be an increase or decrease in his weight? Explain.
Question 31
The weight of a man on the earth is 100 kg. does the weight on the moon increase or decrease?
Question 32
If gravitation is the power by which all bodies tend towards each other, then why do all bodies tend towards the centre of the earth?
Question 33
What is weightlessness?
Question 34
Amit buys few grams of gold at the poles as per the instruction of one his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why?

Question 35
The weight of a body on the surface of the earth is 392 N. what will be the weight of this body on a planet whose mass is double that of the earth and radius is four times that of the earth?
Question 36
If the distance between two masses be increased by a factor of 6, by what factor would the mass of one of them hence to be altered to maintain the same gravitational force?
Question 37
Derive the formula for the gravitational force using the factors on which it depends.
Question 38
Find the gravitational force between the sun and the earth. The mass of the sun is $2.0 \times 10^{30}$ kg, and the mass of the earth is $6.0 \times 10^{24}$ kg. the distance between the sun and the earth is 1.5 \times 1011 m. ($G = 6.67 \times\ {10}^{-11}\ {Nm}^2\ {kg}^{-2}$).
Question 39
Why Newton’s law of gravitation is called the universal law?
Question 40
Write four phenomena which were successfully explained using universal law of gravitation.
Question 41
A flower pot drops from the edge of the roof of a multistoried building. Calculate the time taken by the pot to cross a particular distance AB of height 2.9 m, the upper point A being 19.6 m below the roof.
Question 42
If a ball is thrown straight upwards at a speed of 11 m/sec from balcony, 4 m above the ground, how much time would it take to strike the ground at the base of the balcony?
Question 43
(a) Find the value of acceleration due to gravity at a height of 12,800 km from the surface of the earth. Earth’s radius = 6400 km.
(b) State Newton’s law of gravitation and write the mathematical equation describing it.
Question 44
Show mathematically that acceleration experienced by an object during free fall is independent of mass of the object.
Question 45
Explain why the value of ‘g’ differs while moving from poles to equator on the surface of the earth. State how would its value change on moving:
(i) Towards the centre of the earth.
(ii) Away from the earth.
Question 46
(a) A planet has mass five times of earth and radius three times that of earth. Calculate it a acceleration due to gravity, if the value of ‘g’ on earth is $10 \ ms^{-2}$.
(b) Differentiate between 'G' and 'g'.

Question 47
(a) Differentiate between acceleration due to gravity and universal gravitational constant. Derive a relation between 'g' and 'G'.
(b) State universal law of Gravitation.
Question 48
How does the weight of an object vary with respect to mass and radius of the earth? In a hypothetical case, if the diameter of the earth becomes half of its present value and its mass becomes four times of its present value, then how would the weight of any object on the surface of the earth be affected?
Question 49
(a) Write the formula to find the magnitude of gravitational force between earth and an object on earth’s surface.
(b) Derive how does the value of gravitational force 'F' change between two objects when the
(i) distance between them is reduced to half, and
(ii) mass of one object is increased four times?
Question 50
If the distance between masses of two objects is increased by five units, by what facto would the mass of one of them have to be altered to maintain the same gravitational force? Would there be an increases or a decrease in the mass?

## Summary

This worksheet on gravitation class 9 is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail.