Question:
Define gravity.
Answer:
The force of attraction exerted by the earth on a body is called gravitational pull or gravity.
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.
Why do sewing needles and all pins have a sharp pointed tip?
Q 5.
What is the value of ‘g’ at the centre of Earth ?
Q 6.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 7.
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 8.
Which force is responsible for tides in the ocean at night ?
Q 9.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 10.
What do you mean by acceleration due to gravity ?
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.
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.
Who measured the value of G first time, experimentally?
Q 14.
What do we call the gravitational force between the Earth and an object ?
Q 15.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 16.
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 17.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 18.
Calculate the force of gravitation between two objects of masses 80 kg and 1200 kg kept at a distance of 10 m from eachother.Given, G =
/
.
Q 19.
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 20.
Fill in the blanks :
Assuming negligible air drag, if a steel ball and a table tennis ball are dropped from a height of 100 metres, both will reach the ground at ________ time(s). (same/different)
Q 21.
What is the importance of universal law of gravitation ?
Q 22.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 23.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 24.
Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 10
24 kg and of the Sun = 2 × 10
30 kg. The average distance between the two is 1.5 × 10
11 m.
Q 25.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 26.
Is weight a scalar quantity?
Q 27.
What are Plimsoll Lines?
Q 29.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
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
.
Q 31.
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 32.
State and explain universal law of gravitation.What is its importance ?
Q 33.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 34.
What is value of ‘g’ on Earth ?
Q 35.
Why is G called the Universal Constant?
Q 37.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
Q 38.
A car falls off a ledge and drops to the ground in 0.5 s.Let g =
(for simplifying the calculations).
(i) What is its speed on striking the ground ?
(ii) What is its average speed during 0.5 s ?
(iii) How high is the ledge from the ground ?
Q 39.
Who gave three laws of planetary motion ?
Q 40.
Then why Is the Earth not seen moving towards the stone ?
Q 41.
What is the SI unit of weight ?
Q 42.
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 43.
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/s
2)
Q 45.
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Q 46.
State the universal law of gravitation.
Q 47.
The Earth and the Moon are attracted to each other by gravitational force. Does the Earth attract the Moon with a force that is greater or smaller or the same as the force with which the Moon attracts the Earth ? Why ?
Q 48.
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 49.
What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?
Q 50.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
