## Reference Notes | SLC

Gravity and Gravitation – Exercise for Practice

For: Science Class 10

**Exercise for Practice**

**Answer the following questions. Figure shows the marks for each question in SLC examination.**

- State Newton’s law of gravitation. Calculate the force with which the Moon pulls every kilogram of water in our rivers given that the Moon is 3x 10
^{5}km away from Nepal and the mass of the Moon is 7x 10^{22 }(Ans: 5.18x 10^{-5}N) | [1K+3.5HA = 4.5] - Define acceleration due to gravity ‘g’. Explain why the value of ‘g’ is less at the top of Everest than at its bottom. | [1K+2U =3]
- Mention what is the relation of force of gravitation with masses of the objects and distance. If the mass of a planet is 1.9×10
^{26}kg and radius is 71x 10^{6}What will be the gravitational field intensity of the planet? What will be the weight of a man of mass 60 kg on that planet? (G=6.67×10^{-11}Nm2/kg2) [Ans: 25.13 N/kg, 1507.8N] | [1+3=4] - Write down definition and the unit of acceleration due to gravity ‘g’. Explain why the values of ‘g’ vary from place to place on the earth. [1.5+2=3.5]
- State Newton’s universal law of gravitation. What is the weight of a body during free fall? Prove g α (1/R
^{2}) | [1+0.5+2=3.5] - Weight of an object is greater at the polar region than the equatorial region of earth, why? Calculate the gravitation force in between two objects of mass 25 kg and 20 kg if distance between them is 5m.[2+2=4 ] [Ans: 1.334x 10
^{-9}N] - What is gravity? If mass of the sun is 2x 10
^{33}kg, that of the earth is 6x 10^{24}kg and the distance between them is 1.5x 10^{11 }What is the gravitational force produced between them? (G = 6.67x 10^{-11}Nm2/kg2) | [Ans: 3.557x 10^{22}N] | [1+3=4] - If a body is dropped from the same height once in the equator an d then in the polar region, in which place will it fall faster? Explain with reason. What is weightlessness? Give a condition in which an object becomes weightless. [2+1+0.5=3.5]
- List two differences between universal gravitational constant (G) and acceleration due to gravity (g). The earth’s orbit is oval in shape. Explain how the magnitude of the gravitational force between the earth and the sun changes as the Earth moves from position ‘A’ to ‘B’ as shown in the figure below. [2+1.5=3.5]
- In the formula g= GM/R
^{2}what do G, M and R represent for? Calculate the mass of the Earth assuming that it is a sphere with radius 6.67x 10^{6 }m | 1.5+2.5=4 [Ans: 6.536x 10^{24}Kg] - Weight of a body is found less at the top of the mountain that at the bottom of it, why? The mass and the radius of Jupiter is 1.9×10
^{27}kg and 71x 10^{6}m respectively, find out the acceleration due to gravity in it. [2+2.5=4.5] | [Ans: 25.13 m/s2] - Write down the conclusion obtained from coin and feather experiment. Write down any two differences between mass and weight. [ 1+2=3 ]
- State Newton’s law of gravitation. In which parts of the earth is the true weight of a body maximum and zero? Write two effects of gravity. [ 1+1+1=3 ]
- Define gravitational field intensity. If the mass of the moon is 7.2×10
^{22}Kg and its radius is 1.7×10^{6}m, calculate the gravitational field intensity of the moon. What will the weight of a person with mass 60 kg on the moon be? - Define Newton’s law of gravitation. Why is it called universal law? A man of 75 kg is standing on the surface of the earth having the mass of 6×10
^{24}If the radius of the earth is 6380 km, calculate the force of attraction between man and earth. (G=6.67x 10^{-11}Nm^{2}/kg^{2}) 1+1+2.5 | [Ans: 7.37×10^{2}N] - What is acceleration due to gravity? Establish the relation between due to gravity (g) and radius of the earth
- (R)1+2=3 [G=6.67×10
^{-11}Nm^{2}/ kg^{2}] | [1+2.5+1=4.5] | [Ans:1.6N/Kg, 99.6N] - State Newton’s law of gravitation. Calculate the change in gravitational force between two bodies when the distance between them is made double; keeping their mass constant. [2+2.5=4.5]
- Define free fall? Why the apparent weight of freely falling object is zero? Find the weight of 10 kg object on the surface of the moon. [1+1+1=3] | [Ans:16.6N]
- What is gravity? If an object at a distance 6,400 km from the centre of earth weighs 10N, what will be its weight if it is lifted to 12,800 km from the centre of earth? Give a condition at which an object becomes weightless.
- Write down two differences between weight and mass. If two objects of masses m
_{1}and m_{2}are kept at a distance’d’. Prove that the gravitational force between them (F) = Gm_{1}m_{2}/d^{2}