Gravitation

Q 1.

State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?

Q 2.

Calculate the force of gravitation between the Earth and the Sun,given that the mass of the Earth = $6x1024$ kg and mass of the Sun = $2\; x\; 1030$ kg. The average distance between the two is $1.5x1011$ m.

Q 3.

Can you calculate density of Earth from Newton’s law of gravitation ?

Q 4.

What do we call the gravitational force between the Earth and an object ?

Q 5.

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/s²).

Q 6.

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 = $10\; m/s2$

Q 7.

Fill in the blanks :
________ of an object is the force of gravity acting on it.

Q 8.

Why do sewing needles and all pins have a sharp pointed tip?

Q 9.

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 10.

Fill in the blanks :
Every object in the universe ________ other bodies.

Q 11.

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 12.

What is the value of ‘g’ at the centre of Earth ?

Q 13.

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 14.

What do you mean by acceleration due to gravity ?

Q 15.

Calculate the value of acceleration due to gravity on Moon. Given mass of Moon = $7.4x1022$ kg, radius of Moon = 1740 km

Q 16.

Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 10²⁴ kg and of the Sun = 2 × 10³⁰ kg. The average distance between the two is 1.5 × 10¹¹ m.

Q 17.

What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?

Q 18.

Fill in the blanks :
Weight of an object is the product of ______ and ________.

Q 19.

Write the standard equations of motion when an object is thrown upwards with some initial velocity?

Q 20.

Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.

Q 21.

The mass of Earth is $6x1024$ kg and that of moon is $7.4x1022$ kg. If the distance between the Earth and the Moon is $3.84x105$ km, calculate the force exerted by Earth on the Moon. Given G = $6.7x10-11$ $Nm2/kg2$.

Q 22.

The distance of planet Jupiter from the sun is 5-2 times that of Earth.Find the period of revolution of Jupiter around sun.

Q 23.

Distinguish between gravitation and gravity.

Q 24.

A ball is thrown up with a speed of 15 m/s.How high will it go before it begins to fall ? Take g= $9.8\; m/s2$

Q 25.

Which force is responsible for tides in the ocean at night ?

Q 26.

Explain what is meant by ‘free fall’and acceleration due to gravity.

Q 27.

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 28.

The volume of a 500 g sealed packet is 350 cm³. Will the packet float or sink in water if the density of water is 1 g cm^-3? What will be the mass of the water displaced by this packet?

Q 29.

You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?

Q 30.

To estimate the height of a bridge over a river,a stone is dropped freely on the river from the bridge.The stone takes 2 s to touch the water surface in the river.Calculate the height of the bridge from the water level.Take g = 9.8$m/s2$.

Q 31.

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 32.

What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?

Q 33.

What is the value of G (i) on Earth (ii) on Moon ?

Q 34.

Which force revolves Moon around Earth ?

Q 35.

Does Newton’s third law of motion apply to gravitational force ?

Q 36.

Can a body have weight but no mass ?

Q 37.

How are gravitation and gravity related ?

Q 38.

State and explain universal law of gravitation.What is its importance ?

Q 39.

Fill in the blanks :
The force which keeps the object moving in a circular path is called _____ force. It always acts towards the _____.

Q 40.

Fill in the blanks :
The force of attraction between two objects is ______ proportional to the product of their masses and _____ proportional to the square of a distance between them.

Q 41.

Fill in the blanks :
Kepler's Law of ______ states that a line that connects a planet to the Sun sweeps out equal ______ in the plane of the planet's orbit in _____time intervals.

Q 42.

Fill in the blanks :
The value of g ________ (increases/decreases) as we go downwards from the earth's surface.

Q 43.

Who measured the value of G first time, experimentally?

Q 44.

Does Law of gravitation obey Newton's third law of motion?

Q 45.

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 46.

Define weight? How it is related to mass?

Q 47.

A ball is thrown upwards from the ground of a tower with a speed of 20 m/s. There is a window in the tower at the height of 15m from ground. How many times and when will the ball pass the window? (g = 10 m/s²)

Q 48.

Name the scientist who identified the relation about force of gravitation. Name the law.

Q 49.

Fill in the blanks :
The average acceleration of free fall on the surface of earth is ______ .

Q 50.

Fill in the blanks :
The force of gravity _________ with altitude. It also varies on the surface of the earth, _________ from poles to the equator.