Question:
What happens to 'g' experienced by a body when it moves up the earth's surface?
Answer:
When a body moves up the earth surface, the value of 'g' decreases because its distance from the centre of the earth increases.
Let h = height of the body from the earth's surface and RE is the radius of the earth. Acceleration at height 'h' will be:
gh = GME/(RE+ h)2 = GME/RE2 × RE2/(RE+ h)2
⇒ gh = gRE2/(RE+ h)2 (where g = GME/RE2 = 9.81 m/s2.)
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
Why do sewing needles and all pins have a sharp pointed tip?
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.
Calculate the force of gravitation between the Earth and the Sun,given that the mass of the Earth =
kg and mass of the Sun =
kg. The average distance between the two is
m.
Q 5.
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 6.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
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.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 9.
What is the value of ‘g’ at the centre of Earth ?
Q 10.
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 11.
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 12.
What do you mean by acceleration due to gravity ?
Q 13.
Which force is responsible for tides in the ocean at night ?
Q 14.
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 15.
What do we call the gravitational force between the Earth and an object ?
Q 16.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 17.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 18.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 19.
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 20.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 21.
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 22.
Fill in the blanks :
The value of
g at poles is ______ (lower/higher) than its value at the equator.
Q 23.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 24.
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 25.
Why is the weight of an object on the Moon (l/6)th its weight on the Earth ?
Q 26.
The distance between two objects is doubled. What happens to gravitational force between them
Q 27.
Who measured the value of G first time, experimentally?
Q 28.
An object is placed at the surface of the earth and is at distance R from the center of the earth. The object weighs 180N. What will be its weight if it is at distance 3R from the center of the earth.
Q 29.
What are the differences between the mass of an object and its weight?
Q 31.
The volume of a 500 g sealed packet is 350 cm
3. 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 32.
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 33.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 34.
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 35.
What is the importance of universal law of gravitation ?
Q 36.
What is the acceleration of free fall ?
Q 37.
Which force revolves Moon around Earth ?
Q 38.
Does Newton’s third law of motion apply to gravitational force ?
Q 39.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
Q 40.
A body is just dropped from a height What is its initial velocity ?
Q 41.
Why don’t two objects move towards each other due to gravitational pull between them ?
Q 42.
Can you calculate mass of Earth from Newton’s law of gravitation ?
Q 43.
State and explain universal law of gravitation.What is its importance ?
Q 44.
Compare gravitational force between light objects and heavy objects.
Q 45.
Define g and G.Establish relation between them.
Q 46.
Whenever a body is thrown up with a certain velocity,the upward motion is opposed by gravitational pull of earth and also by the resistance of air.
Therefore, velocity of the body goes on decreasing. When this velocity becomes zero,the body cannot rise further.It has attained,what is called ‘maximum height’.From this height,the body begins to fall downwards under the action of gravity.
Read the above passage and answer the following questions:
(i) At the highest point,what are the velocity and acceleration of the body?
(ii) What is the maximum height attained by a body thrown upwards with a velocity of 19.6 m/s ? Take g =
.
(iii) What values in life do you learn from this concept ?
Q 47.
Fill in the blanks :
The mass of the earth is ________ kg.
Q 48.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 49.
What was heliocentric theory? Who proposed this?
Q 50.
What is retrograde motion of planets (say mars planet)?
