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An iron ball and a wooden ball of the same radius are released from a height ‘h’ in vacuum. The time taken by both of them to reach the ground is

(a) Unequal (b) Exactly equal (c) Roughly equal (d) Zero Answer: b (16)

Two planets have the same average density but their radii are R1 and R2 . If acceleration due to gravity on these planets be g1 and g2 respectively, then

(a) g1/g2 = R1/R2 (b) g1/g2 = R2/R1 (c) g1/g2 = R12/R22 …

The time period of a simple pendulum on a freely moving artificial satellite is

(a) Zero (b) 2 sec (c) 3 sec (d) Infinite Answer: d (15)

If the change in the value of ‘g’ at a height h above the surface of the earth is the same as at a depth x below it, then (both x and h being much smaller than the radius of the earth)

(a) x=h (b) x=2h (c) x=h/2 …

Weightlessness experienced while orbiting the earth in space-ship, is the result of

(a) Inertia (b) Acceleration (c) Zero gravity (d) Free fall towards earth Answer: d (20)

Two identical solid copper spheres of radius R placed in contact with each other. The gravitational attracton between them is proportional to

(a) R2 (b) R–2 (c) R4 (d) R–4 Answer: c (17)

Which of the following statements about the gravitational constant is true

(a) It is a force (b) It has no unit (c) It has same value in all systems of units (d) It depends on the value of the masses (e) It does not depend on the nature of the …

Earth binds the atmosphere because of

(a) Gravity (b) Oxygen between earth and atmosphere (c) Both (a) and (b) (d) None of these Answer: a (12)

Two sphere of mass m and M are situated in air and the gravitational force between them is F. The space around the masses is now filled with a liquid of specific gravity 3. The gravitational force will now be

(a) F (b) F/3 (c) F/9 …

The gravitational force Fg between two objects does not depend on

(a) Sum of the masses (b) Product of the masses (c) Gravitational constant (d) Distance between the masses Answer: a (23)

The force of gravitation is

(a) Repulsive (b) Electrostatic (c) Conservative (d) Non-conservative Answer: c (7)

54. Moment of inertia of a sphere of mass M and radius R is I. Keeping constant if a graph is plotted between I and R, then its form would be

Ans. d (21)

Mass M is divided into two parts xM and (1-x) M . For a given separation, the value of x for which the gravitational attraction between the two pieces becomes maximum is

(a) 1/2 (b) 3/5 (c) 1 …

Two loops P and Q are made from a uniform wire. The radii of P and Q are r1 and r2 respectively, and their moments of inertia are l1 and l2 respectively. If l2/l1=4 then r2/r1 equals

(a) 42/3 (b) 41/3 (c) 4-2/3 (d) 4-1/3 Ans. b (18)

53. Three identical thin rods each of length l and mass M are joined together to form a letter H. What is the moment of inertia of the system about one of the sides of H

(a) Ml2/3 (b) Ml2/4 (c) 2Ml2/3 (d) 4Ml2/3 Ans. d (8)

Reason of weightlessness in a satellite is

(a) Zero gravity (b) Centre of mass (c) Zero reaction force by satellite surface (d) None Answer: c (13)

Who among the following gave first the experimental value of G

(a) Cavendish (b) Copernicus (c) Brook Teylor (d) None of these Answer: a (13)

The moment of inertia of a sphere (mass M and radius R) about it’s diameter is I. Four such spheres are arranged as shown in the figure. The moment of inertia of the system about axis xx’ will be

(a) 3I (b) 5 I (c) 7 I (d) 9 I Ans. d (16)

The centripetal force acting on a satellite orbiting round the earth and the gravitational force of earth acting on the satellite both equal F. The net force on the satellite is

(a) Zero (b) F (c) F √2 (d) 2 Fb Answer: b (16)

The mass of the moon is 7.34×1022 kg and the radius is 1.74×106 m . The value of gravitation force will be

(a) 1.45 N/kg (b) 1.55 N/kg (c) 1.75 N/kg (d) 1.62 N/kg Answer: d (13)

The distance of the centres of moon and earth is D. The mass of earth is 81 times the mass of the moon. At what distance from the centre of the earth, the gravitational force will be zero

(a) D/2 (b) 2D/3 (c) 2D/4 …

50. In a rectangle ABCD (BC=2AB) . The moment of inertia along which axis will be minimum

(a) BC (b) BD (c) HF (d) EG Ans. d (36)

49. Three point masses m1, m2, m3 are located at the vertices of an equilateral triangle of length ‘a’ . The moment of inertia of the system about an axis along the altitude of the triangle passing through m1 is

(a) (m2+m3)a4/4 (b) (m 1+m2+m 3)a2 (c) (m1+m2)a2/2 (d) (m2+m3)a2 Ans. a (46)

The gravitational force between two point masses m1 and m2 at separation r is given by F = k m1 m2/r2 The constant k

(a) Depends on system of units only (b) Depends on medium between masses only (c) Depends on both (a) and (b) (d) Is independent of both (a) and (b) Answer: a (52)

Gravitational mass is proportional to gravitational

(a) Field (b) Force (c) Intensity (d) All of these Answer: d (14)

The earth (mass = 6×10 24 kg ) revolves round the sun with angular velocity 2×10-7 rad/s in a circular orbit of radius 1.5×108 km. The force exerted by the sun on the earth in newtons, is

(a) 18×1025 (b) Zero (c) 27 ×1039 …

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.

(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 …

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

Two particles of equal mass go round a circle of radius R under the action of their mutual gravitational attraction. The speed of each particle is

(a) v = 1/2R √1/gm (b) v =√gm /2R (c) v=1/2√gm/R (d) v=√4gm/R Answer: c (7)

9. Assertion : The slope of momentum versus time curve give us the acceleration. Reason : Acceleration is given by the rate of change of momentum

8. Assertion : Mass is a measure of inertia of the body in linear motion. Reason : Greater the mass, greater is the force required to change its state of rest or of uniform motion.

7. Assertion : No force is required by the body to remain in any state. Reason : In uniform linear motion, acceleration has a finite value.

6. Assertion : Aeroplanes always fly at low altitudes. Reason : According to Newton’s third law of motion, for every action there is an equal and opposite reaction.

5. Assertion : If two objects of different masses have same momentum, the lighter body possess greater velocity. Reason : For all bodies momentum always remains same.

4. Assertion : Force is required to move a body uniformly along a circle. Reason : When the motion is uniform, acceleration is zero.

1. Assertion : Inertia is the property by virtue of which the body is unable to change by itself the state of rest only. Reason : The bodies do not change their state unless acted upon by an unbalanced external force.

Read the assertion and reason carefully to mark the correct option out of the options given below: (a) If both assertion and reason are true and the reason is the correct explanation of the assertion. (b) If both assertion and …