Very Short Answer Type Questions
Q.1. Define free fall.
Ans. It is the fall of a body under the effect of gravity alone.
Q.2. Give an example of motion of an object under the influence of gravitational force on earth.
Ans. Movement of moon around earth.
Q.3. Why the value of g becomes greater at the poles than at the equator?
Ans. The earth is not perfect sphere. The radius of earth increases from the poles to the equator, therefore, value of g becomes greater at the poles than at the equator.
Q.4. Define “universal law of gravitation”.
Ans. It states that the force between tw masses kept a certain distance apart is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.
Q.5. Give reason for the statement that the value of g becomes greater at the poles than at the equator.
Ans. At poles, the radius of the earth is minimum, so the value of g is maximum. At the equator, the radius of earth is maximum, so the value of g is minimum as g =GM/R²
Q.6. The factors associated with the motion of an object are: Force, Velocity, Acceleration and Momentum. Out of these four factors which one remains constant for all bodies – large or small undergoing a free fall?
Ans. During free fall, acceleration remains constant for all bodies large or small.
Q.7. What will be the mass of a body at the centre of the earth as compared to other places on the earth?
Ans. Mass of a body is constant everywhere.
Q.8. Do the gravitational forces obey Newton’s third law of motion ?
Ans. Yes.
Q.9. What is the ratio of forces between two masses kept at certain distance in air to the force between them when kept in any other medium?
Ans. 1:1, because the gravitational force is independent of the nature of medium in which the bodies are placed.
Q.10. Write the expression for the acceleration due to gravity at the surface of the earth.
Ans. g = GM/R2
Q.11. Is it possible to shield a body from gravitational field ?
Ans. No, as the gravitational force is independent of the nature of medium between two bodies
Q.12. If the density of a planet is doubled without changing its radius, how does g on the planet change?
Ans. The acceleration due to gravity gp. Therefore, an increase in the density increases the value of g.
Q.13. Does the acceleration with which a body falls towards the centre of the earth depend upon its mass?
Ans. The acceleration due to gravity is independent of the mass of the body as g = GM/R² where M stands for the mass of the planet.
Q.14. Has gravity any effect on inertial mass?
Ans. No.
Q.15. On what factor does the value of acceleration due to gravity depend?
Ans. The value of acceleration due to gravity depends upon (i) shape and rotation of the earth. (ii) latitude (iii) altitude or height and (iv) depth.
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