Question:
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.
Answer:
20N. [Hint: See logic in Q16-9(i)]
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
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 3.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 4.
What do we call the gravitational force between the Earth and an object ?
Q 5.
What is the value of ‘g’ at the centre of Earth ?
Q 6.
What do you mean by acceleration due to gravity ?
Q 7.
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 8.
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 9.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 10.
Why do sewing needles and all pins have a sharp pointed tip?
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.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 13.
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 14.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 15.
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 16.
Is weight a scalar quantity?
Q 17.
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 18.
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 19.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 20.
The distance between two objects is doubled. What happens to gravitational force between them
Q 21.
Can a body have mass but no weight ?
Q 22.
Compare gravitational force between light objects and heavy objects.
Q 23.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 24.
What are the Kepler Laws that govern the motion of the planets?
Q 25.
Who measured the value of G first time, experimentally?
Q 26.
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 27.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 29.
Fill in the blanks :
A body is said to be in _______ when only gravity acts on it.
Q 30.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 31.
Fill in the blanks :
The SI unit of mass is ______.
Q 32.
Fill in the blanks :
It is the ____________ of the earth, which holds our atmosphere in place.
Q 33.
Why does an object float or sink when placed on the surface of the water?
Q 34.
In what direction does the buoyant force on an object immersed in a liquid act?
Q 35.
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 36.
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Q 37.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 38.
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 39.
What are the differences between the mass of an object and its weight ?
Q 40.
What is the magnitude of the gravitational force between the Earth and a 1 kg on its surface ? (Mass of the Earth Is
kg and radius of the Earth is
m.)
Q 41.
Who explained the motion of planets around the Sun ?
Q 42.
Can a body have weight but no mass ?
Q 43.
Define g and G.Establish relation between them.
Q 44.
On earth,value of G =
.What is its value on moon,where g is nearly
th that of earth ?
Q 45.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 46.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 47.
Fill in the blanks :
The SI unit of weight is _____.
Q 48.
What was heliocentric theory? Who proposed this?
Q 49.
State the universal law of gravitation.
Q 50.
Why is G called the Universal Constant?
