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.
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.
Which force is responsible for tides in the ocean at night ?
Q 7.
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 8.
What do we call the gravitational force between the Earth and an object ?
Q 9.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 10.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 11.
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 12.
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 13.
What do you mean by acceleration due to gravity ?
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.
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.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 18.
What is the importance of universal law of gravitation ?
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 happens to 'g' experienced by a body when it moves up the earth's surface?
Q 21.
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 22.
What are Plimsoll Lines?
Q 23.
What is value of ‘g’ on Earth ?
Q 25.
Is weight a scalar quantity?
Q 26.
What is the SI unit of weight ?
Q 27.
Distinguish between mass and weight.
Q 28.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 29.
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 30.
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 31.
State and explain universal law of gravitation.What is its importance ?
Q 32.
Why is G called the Universal Constant?
Q 33.
Can a body have weight but no mass ?
Q 34.
Fill in the blanks :
______ stated that every planet moves around the sun in closed elliptical orbit, with the ___ at one focus.
Q 35.
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 36.
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 37.
Then why Is the Earth not seen moving towards the stone ?
Q 38.
Fill in the blanks :
When objects of different masses and sizes are dropped from same height would reach the ground at ______ (same time/different times), considering negligible air resistance.
Q 39.
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 40.
A stone drops from the edge of the roof.It passes a window 2 m high in 0.1 s.How far is the roof above the top of the window
Q 41.
Who gave three laws of planetary motion ?
Q 42.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
Q 43.
A body is just dropped from a height What is its initial velocity ?
Q 44.
A body weighs 10 kg on the surface of earth.What would be its mass and weight at the centre of earth ?
Q 45.
Distinguish between gravitation and gravity.
Q 46.
In Fig.,the line that joins a planet to the sun sweeps out areas
,
in time intervals 6 weeks,3 weeks and 2 weeks respectively.How are
,
realted ?
Q 47.
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 48.
What is the importance of Universal Law of Gravitation?
OR
Q: State any one phenomena related to the Universal Law of Gravitation.
Q 49.
An object moves in a circular motion due to centripetal force, acting towards the center. The moon also rotates around the earth? Does centripetal force acts on it? Why does the moon not fall on the earth?
OR
Q:If the moon attracts the earth, why does the earth not move towards the moon?
