Question:
If the moon attracts the Earth,why does the Earth not move towards the Moon ?
Answer:
The force exerted by the Earth on Moon is used in changing the path of Moon from straight line to circular path.The Moon attracts the Earth with the same force.But the Earth is too heavy to move towards the Moon.Rather,we can show that distance moved by Earth towards the Moon is so small that it cannot be detected.
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
A particle is dropped from a tower 180 m high.How long does it take to reach the ground ? What is the velocity when it touches the ground ? Take g =
Q 3.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 4.
A boy on a clif£ 49 m high drops a stone.One second later,he throws a second stone after the first.They both hit the ground at the same time. With what speed did he throw the second stone ?
Q 5.
Why do sewing needles and all pins have a sharp pointed tip?
Q 6.
Which force is responsible for tides in the ocean at night ?
Q 7.
What is the value of ‘g’ at the centre of Earth ?
Q 8.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 9.
What do you mean by acceleration due to gravity ?
Q 10.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 11.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 12.
Two stones A and B are dropped from a multistoried building. A is dropped from 100 m and after some time B is dropped from 50 m height. Both of them reach the earth at the same time. Will they have equal velocity while reaching the ground ? Calculate and find out the answer (take g =10 m/s
2).
Q 13.
The mass of Earth is
kg and that of moon is
kg. If the distance between the Earth and the Moon is
km, calculate the force exerted by Earth on the Moon. Given G =
.
Q 14.
Who measured the value of G first time, experimentally?
Q 15.
At what height above the surface of the earth, the value of 'g' becomes 64% of its value at the surface of the earth. Take radius of the earth = 6400 km.
Q 16.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 17.
Why is G called the Universal Constant?
Q 18.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
Q 19.
State the universal law of gravitation.
Q 20.
What is the SI unit of weight ?
Q 22.
Loaded test-tube placed in pure milk sinks to a certain mark (M). Now some water is mixed with the milk. Will the test tube sink more or less? Explain.
Q 23.
Gravitational force acts on all objects in proportion to their masses.Why then,a heavy object does not fall faster than a light object ?
Q 24.
What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?
Q 25.
Which force accelerates a body in free fall ?
Q 26.
Does Newton’s third law of motion apply to gravitational force ?
Q 27.
What is value of ‘g’ on Earth ?
Q 28.
A body weighs 10 kg on the surface of earth.What would be its mass and weight at the centre of earth ?
Q 29.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 30.
Fill in the blanks :
Acceleration due to gravity (g) is _______ (dependent/independent) of mass.
Q 31.
How is gravitational force of attraction between two bodies affected if(i) Mass of both bodies is doubled.(ii) Distance between them is halved.
Q 32.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 34.
Amit buys few grams of gold at the poles as per the instruction of one of 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? [Hint: The value of g is greater at the poles than at the equator].
Q 35.
A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground.
Q 36.
A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s
2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?
Q 38.
Is weight a scalar quantity?
Q 39.
Fill in the blanks :
The acceleration which causes changes only in direction of the velocity of a body is called __________ and it is always directed ___________ the circle.
Q 40.
Fill in the blanks :
During free fall condition, the body is in state of __________.
Q 41.
Relative density of silver is 10.8. If the density of water is 10
3kg/m
3, find density of silver.
Q 42.
The gravitational force between two objects is 100 N. How should the distance between these objects be changed so that force between them becomes 50 N ?
Q 43.
Two bodies A and B having masses 2 kg and 4 kg respectively are separated by 2 m.Where should a body of mass 1 kg be placed so that the gravitational force on this body due to bodies A and B is zero ?
Q 44.
If the distance between two masses is increased by a factor of 4,by what factor would the mass of one of them have to be altered to maintain the same gravitational force ?
Q 45.
A force of 20 N acts upon a body whose weight is 9.8 N.What is the mass of the body and how much is its acceleration ?
Q 46.
Suppose a planet exists whose mass and radius both,are half those of Earth.Calculate the acceleration due to gravity on the surface of this planet.
Q 47.
What is the importance of universal law of gravitation ?
Q 48.
What is the acceleration of free fall ?
Q 49.
A stone is released from the top of a tower of height 19.6 m.Calculate its final velocity just before touching the ground.
Q 50.
A stone is thrown vertically upward with an initial velocity of 40 m/s.Taking g =
,find the maximum height reached by the stone.What is the net displacement and the total distance covered by the stone ?
