Question:
Which force accelerates a body in free fall ?
Answer:
The force of gravity of Earth.
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.
Which force is responsible for tides in the ocean at night ?
Q 6.
What is the value of ‘g’ at the centre of Earth ?
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.
Can you calculate density of Earth from Newton’s law of gravitation ?
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.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 11.
What do you mean by acceleration due to gravity ?
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 we call the gravitational force between the Earth and an object ?
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.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 17.
Who measured the value of G first time, experimentally?
Q 18.
What is the importance of universal law of gravitation ?
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.
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 21.
What is value of ‘g’ on Earth ?
Q 23.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 24.
What are Plimsoll Lines?
Q 25.
What is the SI unit of weight ?
Q 26.
Is weight a scalar quantity?
Q 27.
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 28.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 29.
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 30.
Does value of ‘g’ vary from place to place on Earth ?
Q 31.
Distinguish between mass and weight.
Q 32.
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 33.
Why is G called the Universal Constant?
Q 34.
Where is ‘g’greater, at poles or at equator ?
Q 35.
Can a body have mass but no weight ?
Q 37.
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 38.
Why is the weight of an object on the Moon (l/6)th its weight on the Earth ?
Q 39.
Then why Is the Earth not seen moving towards the stone ?
Q 40.
A body is just dropped from a height What is its initial velocity ?
Q 41.
In free fall, will heavier objects accelerate more than light ones ?
Q 42.
State and explain universal law of gravitation.What is its importance ?
Q 43.
Fill in the blanks :
______ stated that every planet moves around the sun in closed elliptical orbit, with the ___ at one focus.
Q 44.
What is the importance of Universal Law of Gravitation?
OR
Q: State any one phenomena related to the Universal Law of Gravitation.
Q 45.
Does Law of gravitation obey Newton's third law of motion?
Q 46.
Fill in the blanks :
The acceleration which causes changes only in direction of the velocity of a body is called __________ and it is always directed ___________ the circle.
Q 47.
Fill in the blanks :
During free fall condition, the body is in state of __________.
Q 48.
Fill in the blanks :
Universal gravitational constant G = _____________.
Q 49.
Why does a block of plastic released under water come up to the surface of the water?
Q 50.
A ball of mass 4kg and density 4000 kgm
3 is completely immersed in water. Find the buoyant force acting on ball if the density of water is 10
3kg/m
3. (Take g = 10ms
-2)
