Force

1. What is gravitational force? Write down its SI unit and mention any two importance of it.
2. What are the factors affecting gravitational force? Who developed the value of G?
3. State and prove Newton’s law of gravitation.
4. Why is gravitational law also called universal law?
5. What is gravitational constant? Write down its value.
6. Value of G is 6.67 x 10-11Nm2/kg2. What does it mean? Gravitational constant is also called
universal constant. Why?
7. At what condition is the value of gravitational force equal to gravitational constant? Show with
calculation
8. What gravity? Write any three effects of gravity. Differentiate between gravity and gravitational
force.
9. Write any two differences between mass and weight. Mass is constant but weight is variable.
Why?
10. What happens to the force of attraction between two bodies if
a) Distance between them is doubled
b) Mass of both bodies are doubled and distance between them is also doubled,
c) Distance between them is halved
11. What is acceleration due to gravity? Prove g∞1/R2
12. Give reasons
a) Value of g changes from place to place. Why?
b) Value of g is more at poles than at the equator. Why?
c) Weight of an object is more at terai than at the mountain. Why?
d) There is use of parachute on the moon. Why?
e) A paratrooper can land safely while jumping from an aero plane on earth.
f) Jumping from a significant height may cause injury. Why?
g) One will have an eerie feeling when he/she moves down while playing a rote ping
h) As you climb Mount Everest, the weight of the goods that you carry decreases.
i) When a marble and a feather are dropped simultaneously in a vacuum, they reach the ground
together
13. Write two differences between acceleration due to gravity and gravitational constant.
14. Value of g on the surface of the earth is 9.8m/s2. What does it mean?
15. Write down the value of g on the poles and equator of the earth and moon and Jupiter.
16. A student suggests a trick for gaining profit in a business. He suggests buying oranges from the
mountain selling them to terai at the cost price. If a beam balance is used during this transaction,
explain based on scientific fact, whether his trick goes wrong or right.
17. Among the objects dropped from the same height in the polar region and the equatorial region of
the earth, where will the object fall faster? Why?
18. Out of two paper sheets, one is folded to form a ball. If the paper ball and the sheet of paper are
dropped simultaneously in the air, the folded paper will fall faster. Why?
19. . Why?
20. Write down the conclusion of feather and coin experiment.
21. What is free fall? Define weightlessness. Write any two conditions for weightlessness.
Numerical Problems
1. The mass of Jupiter is 1.92 x 1027kg and that of the sun is 2 x 1030kg. If the magnitude of the
gravitational force between these two masses is 4.166 x 1023N, find the distance between their
centers. [7.8 x 1011m]
2. The mass of earth is 6 x 1024 kg and its radius is 6400km. What will be the gravity of the earth
to a body of mass 1kg on the surface of the earth? [9.8N]
3. The mass of Jupiter is 1.92 x 1027kg and its radius is 7.1 x 107m. What is the acceleration due to
gravity of Jupiter? Also, calculate the weight of a stone of mass 15kg on the surface of Jupiter.
[25m/s2, 375N]
4. What is the acceleration due to gravity on the surface of the earth when its mass is 6 x 1024 kg
and radius 6400km? [9.8m/s2]
5. Calculate the acceleration due to gravity on the top of the Mt Everest of height 8848m from the
sea level. Mass of earth is 6 x 1024 kg and radius 6400km. [9.77m/s2]
6. The acceleration due to gravity of the earth is 9.8m/s2. If the mass of Jupiter is 319 times the
mass of the earth and its radius is 11 times the radius of earth, calculate the acceleration due to
gravity of Jupiter. What is the weight of an object of mass 100kg on Jupiter? [25.83m/s2,
2583N]
7. A person can lift 100kg mass on the surface of the earth. What is the mass he can lift on the
surface of the moon? [586.8kg]
8. The masses of the earth and the sun are 6 x 1024 kg and 2 x 1030kg respectively. If the distance
between their centers is 1.5 x 1011m. calculate the gravitational force between them.
[3.56 x 1022N]
9. Two bodies with the mass of 200kg each are kept at a distance of 2m apart from their centers
on the surface of the earth. Calculate the force of attraction produced between them. [6.67 x
10-7N]
10. When a stone is dropped form a bridge over a river into the water, the sound of the stone
hitting the surface of the water is heard after 2 seconds, calculate the height of the bridge
above the surface of the water. [19.6m]
11. A cricket ball is thrown vertically upwards into the sky reaches a height of 30m. calculate the
velocity with which it is thrown and the time taken to reach the maximum height. [24.25m/s,
2.47s]
12. What will be weight of a man on the moon if his weight on earth is 750N?
13. A cricket ball is thrown vertically upwards into the sky with a velocity of 15m/s, to what
maximum height will the ball reach? [11.47m]
14. If a stone is dropped from a height of 15m, how long will it take to reach the ground?
Calculate the velocity of the stone when it hits the ground. [1.75s, 17.15m/s]