PhysicsFlame Institute

An object weights 72 N on earth. Its weight at a height of R/2 from earth is

(a) 32 N (b) 56 N (c) 72 N (d) Zero Answer: a (5)

The height of the point vertically above the earth’s surface, at which acceleration due to gravity becomes 1% of its value at the surface is (Radius of the earth = R)

(a) 8 R (b) 9 R (c) 10 R (d) 20 R Answer: b (7)

If the Earth losses its gravity, then for a body

(a) Weight becomes zero, but not the mass (b) Mass becomes zero, but not the weight (c) Both mass and weight become zero (d) Neither mass nor weight become zero Answer: a (7)

At what height from the ground will the value of ‘g’ be the same as that in 10 km deep mine below the surface of earth

(a) 20 km (b) 10 km (c) 15 km (d) 5 km Answer: a (9)

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.

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)

A satellite revolves around the earth in an elliptical orbit. Its speed

(a) Is the same at all points in the orbit (b) Is greatest when it is closest to the earth (c) Is greatest when it is farthest from the earth (d) Goes on increasing or decreasing continuously depending upon the …

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.

A small satellite is revolving near earth’s surface. Its orbital velocity will be nearly

(a) 8 km/sec (b) 11.2 km/sec (c) 4 km/sec (d) 6 km/sec Answer: a (11)

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)

Two satellites A and B go round a planet P in circular orbits having radii 4R and R If the speed of the satellite A is 3V, the speed of the satellite B will be.

(a) 12 V (b) 6 V (c) 4/3 V (d) 3/2V Answer: b (7)

The relay satellite transmits the T.V. programme continuously from one part of the world to another because its

(a) Period is greater than the period of rotation of the earth (b) Period is less than the period of rotation of the earth about its axis (c) Period has no relation with the period of the earth about its …

11. If a satellite is orbiting the earth very close to its surface, then the orbital velocity mainly depends on

(a) The mass of the satellite only (b) The radius of the earth only (c) The orbital radius only (d) The mass of the earth only Answer: b (8)

The period of a satellite in a circular orbit around a planet is independent of

(a) The mass of the planet (b) The radius of the planet (c) The mass of the satellite (d) All the three parameters (a), (b) and (c) Answer: c (9)

The mean radius of the earth is R, its angular speed on its own axis is ω and the acceleration due to gravity at earth’s surface is g. The cube of the radius of the orbit of a geostationary satellite will be

(a) R2g/ ω (b) R2 ω2/g (c) Rg/ ω2 …

25. Orbital velocity of earth’s satellite near the surface is 7 km/s. When the radius of the orbit is 4 times than that of earth’s radius, then orbital velocity in that orbit is

(a) 3.5 km/s (b) 7 km/s (c) 72 km/s (d) 14 km/s Answer: a (14)

The time period of a geostationary satellite is

(a) 24 hours (b) 12 hours (c) 365 days (d) One month Answer: a (13)

Orbital velocity of an artificial satellite does not depend upon

(a) Mass of the earth (b) Mass of the satellite (c) Radius of the earth (d) Acceleration due to gravity Answer: b (13)

A satellite is moving around the earth with speed v in a circular orbit of radius r. If the orbit radius is decreased by 1%, its speed will

(a) Increase by 1% (b) Increase by 0.5% (c) Decrease by 1% (d) Decrease by 0.5% Answer: b (4)

Out of the following, the only incorrect statement about satellites is

(a) A satellite cannot move in a stable orbit in a plane passing through the earth’s centre (b) Geostationary satellites are launched in the equatorial plane (c) We can use just one geostationary satellite for global communication around the globe …

Choose the correct statement from the following : The radius of the orbit of a geostationary satellite depends upon

(a) Mass of the satellite, its time period and the gravitational constant (b) Mass of the satellite, mass of the earth and the gravitational constant (c) Mass of the earth, mass of the satellite, time period of the satellite and …

If the height of a satellite from the earth is negligible in comparison to the radius of the earth R, the orbital velocity of the satellite is

(a) gR (b) gR/2 (c) √g/R (d) √gR Answer: d (3)

In a satellite if the time of revolution is T, then K.E. is proportional to

(a) 1/T (b) 1/T2 (c) 1/T3 (d) T-2/3 Answer: d (32)

The orbital velocity of an artificial satellite in a circular orbit just above the earth’s surface is v. For a satellite orbiting at an altitude of half of the earth’s radius, the orbital velocity is

(a) 3/2 v (b) √(3/2) v (c) √(2/3) v (d) 2/3 v Answer: c (5)

26. Two identical satellites are at R and 7R away from earth surface, the wrong statement is (R = Radius of earth)

(a) Ratio of total energy will be 4 (b) Ratio of kinetic energies will be 4 (c) Ratio of potential energies will be 4 (d) Ratio of total energy will be 4 but ratio of potential and kinetic energies will …

Physics

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