Class 9th | chap 5 | Gravitation | Full Conceptual Q's. | Q.s 1 to Q's 9 |

Описание: Class 9th | chap 5 | Gravitation | Full Conceptual Qs. | Q.s 1 to Qs 9 | #conceptualquestions

Q1. If there is an attractive force between all objects, why don’t we feel ourselves gravitating toward nearby massive buildings?
Ans. Gravitational force pulls us to massive buildings but the forces are relatively small due to the small masses of us and buildings when compared to the mass of the earth. Therefore, the attractive force would be almost unnoticeable.

Q2. Does the sun exert a larger force on the Earth than that exerted on the sun by the earth? Explain.

Ans. By Newton’s third law, the force exerted on the Sun by the Earth is exactly equal to the force the Sun exerts on the Earth but in opposite direction.

Q3. What is the importance of gravitational constant ‘G’? Why is it difficult to calculate?
Ans. Constant always play an important in bringing the equality in the dimensions on both sides of an equation and its value depends upon the factors relating the interaction between the two bodies similar is the case with gravitational constant ‘G’ here it maintains the equality on both sides of the universal gravitational law’s equation. It’s difficult to calculate it because there’s no theoretical derivation to it is just an experimentally measured value.

Q4. If Earth somehow expanded to a larger radius, with no charge in mass, how would your weight be affected? How would it be affected if earth instead shrunk?
Ans: According to law of universal Gravitation

F= 𝐺𝑚𝑚𝐸. 𝐸q------------ (i)

As we know that
F=W=mg So eq (i) becomes
mg = 𝐺𝑚𝑚𝐸
𝐸

g = 𝐺𝑚𝐸
𝐸

------------ (ii)

From eq (ii), we say that force of gravity is inversely proportional to the radius of earth. So if radius of Earth gets larger weight would get smaller. If the earth shrunk, the radius of earth decreases and as a result weight gets increases.
Q5. What would happen to your weight on earth if the mass of the earth doubled but its radius stayed the same?
Ans: As we know that

g= 𝐺𝑚𝐸. 𝐸q------------ (i)

Above eq (i) shows that value of ‘g’ depends on mass of earth ‘𝑚𝐸’ and radius of earth ‘𝑟𝐸 ’. If we only double the mass of earth the value of ‘g’ becomes double and weight depends on the value of ‘g’. i.e.
Eq (ii) shows that if value of ‘g’ is doubled, the weight will also double.

Q6. Why lighter and heavier objects fall at the same rate toward the earth?
Ans: Because value of ‘g’ does not depend upon the mass of the body, it depends only on mass of earth and radius of earth. Therefore, lighter and heavier bodies fall towards earth with same acceleration.

Q7. The value of ‘g’ changes with location on earth, however we take the same value of ‘g’ as 9.8ms-2 for ordinary calculations why?
Ans: The value of ‘g’ depends upon the distance from the centre of earth. Greater the distance from the centre of earth, smaller will be the value of ‘g’ and vice versa. The change in the value of ‘g’ is significant only at very large distance. Therefore, we take same value of ‘g’ for ordinary calculation.

Q8. Moon is attracted by the earth, why it does not fall on earth?
Ans: The moon is natural satellite of the earth. It revolves around the earth in a specific orbit. The earth attracts the moon towards itself with gravitational force. The gravitational force of earth provides necessarily centripetal force which compels the moon to move in the circular path. Because of this orbital motion moon does not fall on earth.

Q9. Why for some height larger and smaller satellites must have same orbital speeds?

The orbital speed depends upon the mass of earth and distance from the centre of earth to the centre of mass of satellite and does not depend upon the mass of satellite. Therefore, for some particular distance from the centre of earth, all the satellites have the same orbital speed irrespective of the size of satellite.