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Acceleration due to gravity is ‘g’ on the surface of the earth. The value of acceleration due to gravity at a height of 32 km above earth’s surface is (Radius of the earth = 6400 km)

(a) 0.9 g (b) 0.99 g (c) 0.8 g (d) 1.01 g Answer: b (10)

What should be the velocity of earth due to rotation about its own axis so that the weight at equator become 3/5 of initial value. Radius of earth on equator is 6400 km

(a) 7.4 × 10-4 rad /sec (b) 6.7 × 10-4 rad /sec (c) 7.8 × 10-4 rad /sec (d) 8.7 10-4 …

Mass of moon is 7.34 ×1022 kg. If the acceleration due to gravity on the moon is 1.4 m/s2 , the radius of the moon is (G = 6.667×10-11 Nm2 /kg2)

(a) 0.56 × 104 (b) 1.87 × 106 (c) 1.92 × 106 (d) 1.01 × 108 Answer: b (6)

If mass of a body is M on the earth surface, then the mass of the same body on the moon surface is

(a) M/6 (b) Zero (c) M (d) None of these Answer: c (5)

If radius of the earth contracts 2% and its mass remains the same, then weight of the body at the earth surface

(a) Will decrease (b) Will increase (c) Will remain the same (d) None of these Answer: b (13)

If the radius of the earth shrinks by 1.5% (mass remaining same), then the value of acceleration due to gravity changes by

(a) 1% (b) 2% (c) 3% (d) 4% Answer: c (5)

Where will it be profitable to purchase 1 kilogram sugar

(a) At poles (b) At equator (c) At 45° latitude (d) At 40° latitude Answer: b (8)

24. Assertion : A body subjected to three concurrent forces cannot be in equilibrium. Reason : If large number of concurrent forces acting on the same point, then the point will be in equilibrium, if sum of all the forces is equal to zero.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. (b) If both assertion and reason are true but reason is not the correct explanation of the assertion. (c) If assertion is …

25. Assertion : Impulse and momentum have different dimensions. Reason : From Newton’s second law of motion, impulse is equal to change in momentum.

23. Assertion : A table cloth can be pulled from a table without dislodging the dishes. Reason : To every action there is an equal and opposite reaction.

22. Assertion : A reference frame attached to earth is an inertial frame of reference. Reason : The reference frame which has zero acceleration is called a non inertial frame of reference.

21. Assertion : Newton’s third law of motion is applicable only when bodies are in motion. Reason : Newton’s third law applies to all types of forces, e.g. gravitational, electric or magnetic forces etc.

Let g be the acceleration due to gravity at earth’s surface and K be the rotational kinetic energy of the earth. Suppose the earth’s radius decreases by 2% keeping all other quantities same, then

(a) g decreases by 2% and K decreases by 4% (b) g decreases by 4% and K increases by 2% (c) g increases by 4% and K increases by 4% (d) g decreases by 4% and K increases by 4% …

Radius of earth is around 6000 km. The weight of body at height of 6000 km from earth surface becomes

(a) Half (b) One-fourth (c) One third (d) No change Answer: b (10)

20. Assertion : Linear momentum of a body changes even when it is moving uniformly in a circle. Reason : In uniform circular motion velocity remain constant.

19. Assertion : The acceleration produced by a force in the motion of a body depends only upon its mass. Reason : Larger is the mass of the body, lesser will be the acceleration produced.

18. Assertion : A player lowers his hands while catching a cricket ball and suffers less reaction force. Reason : The time of catch increases when cricketer lowers its hand while catching a ball.

17. Assertion : In the case of free fall of the lift, the man will feel weightlessness. Reason : In free fall, acceleration of lift is equal to acceleration due to gravity.

16. Assertion : When the lift moves with uniform velocity the man in the lift will feel weightlessness. Reason : In downward accelerated motion of lift, apparent weight of a body decreases.

Weight of 1 kg becomes 1/6 on moon. If radius of moon is 1.768× 106m , then the mass of moon will be

(a) 1.99×1030 kg (b) 7.56×1022 kg (c) 5.98 ×1024 kg (d) 7.65×1022 kg Answer: d (5)

15. Assertion : The apparent weight of a body in an elevator moving with some downward acceleration is less than the actual weight of body. Reason : The part of the weight is spent in producing downward acceleration, when body is in elevator.

14. Assertion : A rocket works on the principle of conservation of linear momentum. Reason : Whenever there is a change in momentum of one body, the same change occurs in the momentum of the second body of the same system but in the opposite direction.

13. Assertion : A bullet is fired from a rifle. If the rifle recoils freely, the kinetic energy of rifle is more than that of the bullet. Reason : In the case of rifle bullet system the law of conservation of momentum violates.

12. Assertion : Linear momentum of a body changes even when it is moving uniformly in a circle. Reason : Force required to move a body uniformly along a straight line is zero.

11. Assertion : The work done in bringing a body down from the top to the base along a frictionless incline plane is the same as the work done in bringing it down the vertical side. Reason : The gravitational force on the body along the inclined plane is the same as that along the vertical side.

10. Assertion : A cyclist always bends inwards while negotiating a curve. Reason : By bending, cyclist lowers his centre of gravity.

If the angular speed of the earth is doubled, the value of acceleration due to gravity (g) at the north pole

(a) Doubles (b) Becomes half (c) Remains same (d) Becomes zero Answer: C (60)

Spot the wrong statement :The acceleration due to gravity ‘g’ decreases if

(a) We go down from the surface of the earth towards its centre (b) We go up from the surface of the earth (c) We go from the equator towards the poles on the surface of the earth (d) The …

At the surface of a certain planet, acceleration due to gravity is one-quarter of that on earth. If a brass ball is transported to this planet, then which one of the following statements is not correct

(a) The mass of the brass ball on this planet is a quarter of its mass as measured on earth (b) The weight of the brass ball on this planet is a quarter of the weight as measured on earth …

At what altitude in metre will the acceleration due to gravity be 25% of that at the earth’s surface (Radius of earth = R metre)

(a) 1/4 R (b) R (c) 3/8 R …

R is the radius of the earth and ω is its angular velocity and gp is the value of g at the poles. The effective value of g at the latitude λ = 60° will be equal to

(a) gp – 1/4 Rω2 (b) gp – 3/4 Rω2 (c) gp – Rω2 (d) gp + 1/4 Rω2 Answer: …

The diameters of two planets are in the ratio 4 : 1 and their mean densities in the ratio 1 : 2. The acceleration due to gravity on the planets will be in ratio

(a) 1 : 2 (b) 2 : 3 (c) 2 : 1 (d) 4 : 1 Answer: …

At what height over the earth’s pole, the free fall acceleration decreases by one percent (assume the radius of earth to be 6400 km)

(a) 32 km (b) 80 km (c) 1.253 km (d) 64 km Answer: a …

The depth d at which the value of acceleration due to gravity becomes 1/n times the value at the surface, is [R = radius of the earth]

(a) R/N (b) R ( n-1/n ) (c) R/n2 …

The moon’s radius is 1/4 that of the earth and its mass is 1/80 times that of the earth. If g represents the acceleration due to gravity on the surface of the earth, that on the surface of the moon is

(a) g/4 (b) g/5 (c) g/6 (d) g/8 Answer: b (4)

If the earth suddenly shrinks (without changing mass) to half of its present radius, the acceleration due to gravity will be

(a) g/2 (b) 4g (c) g/4 (d) 2g Answer: b (10)

A spring balance is graduated on sea level. If a body is weighed with this balance at consecutively increasing heights from earth’s surface, the weight indicated by the balance

(a) Will go on increasing continuously (b) Will go on decreasing continuously (c) Will remain same (d) Will first increase and then decrease Answer: b (9)

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