Question:
Write down the equations of motion of objects under the influence of gravitational force of Earth.Explain the meaning of the symbols used.
Answer:
Refer to Art 3.16,Page 162.
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 3.
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 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.
What do you mean by acceleration due to gravity ?
Q 8.
Which force is responsible for tides in the ocean at night ?
Q 9.
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 10.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 11.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
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.
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 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.
Who measured the value of G first time, experimentally?
Q 17.
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 18.
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 19.
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 20.
What is the importance of universal law of gravitation ?
Q 21.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 22.
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 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.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 25.
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 28.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go downwards from the earth's surface.
Q 29.
Is weight a scalar quantity?
Q 30.
What are Plimsoll Lines?
Q 31.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 32.
A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet
Q 33.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 34.
Why is G called the Universal Constant?
Q 35.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 36.
What is value of ‘g’ on Earth ?
Q 37.
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 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.
State and explain universal law of gravitation.What is its importance ?
Q 41.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 42.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
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 44.
What do you mean by Thrust or Buoyant force?
Q 45.
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 46.
State the universal law of gravitation.
Q 47.
Then why Is the Earth not seen moving towards the stone ?
Q 48.
Can a body have mass but no weight ?
Q 49.
Fill in the blanks :
The value of
g at poles is ______ (lower/higher) than its value at the equator.
Q 50.
Fill in the blanks :
A body is said to be in _______ when only gravity acts on it.
