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52. If the density of the material increases, the value of Young’s modulus

(a) Increases (b) Decreases (c) First increases then decreases (d) First decreases then increases Answer-a (18)

51. The longitudinal strain is only possible in

(a) Gases (b) Fluids (c) Solids (d) Liquids Answer-c (11)

49.The quality of the material which opposes the change in shape, volume or length is called

(a) Intermolecular repulsion (b) Intermolecular behaviour (c) Viscosity (d) Elasticity Answer-d (8)

Given mass of the moon is 1/81 of the mass of the earth and corresponding radius is 1/4 of the earth. If escape velocity on the earth surface is 11.2 km/s, the value of same on the surface of the moon is

(a) 0.14 km/s (b) 0.5 km/s (c) 2.5 km/s (d) 5 km/s Answer: c (4)

47. When compared with solids and liquids, the gases have

(a) Minimum volume elasticity (b) Maximum volume elasticity (c) Maximum Young’s modulus (d) Maximum modulus of rigidity Answer-a (13)

The escape velocity of a body on the surface of the earth is 11.2 km/s. If the earth’s mass increases to twice its present value and the radius of the earth becomes half, the escape velocity would become

(a) 5.6 km/s (b) 11.2 km/s (remain unchanged) (c) 22.4 km/s (d) 44.8 km/s Answer: c (5)

The escape velocity on earth is 11.2 km/s. On another planet having twice radius and 8 times mass of the earth, the escape velocity will be

(a) 3.7 km/s (b) 11.2 km/s (c) 22.4 km/s (d) 43.2 km/s Answer: c (5)

45. In suspended type moving coil galvanometer, quartz suspension is used because

(a) It is good conductor of electricity (b) Elastic after effects are negligible (c) Young’s modulus is greater (d) There is no elastic limit Answer-b (12)

145. A disc of mass M and radius R rolls in a horizontal surface and then rolls up an inclined plane as shown in the fig. If the velocity of the disc is v, the height to which the disc will rise will be

(a) 3v2/ 2g (b) 3v2/4g (c) v2/4g (d) v2/2g Ans. b (55)

37.The ratio of diameters of two wires of same material is n : 1. The length of wires are 4 m each. On applying the same load, the increase in length of thin wire will be

(a) n2 times (b) n times (c) 2n times (d) None of the above Answer-a (10)

41. Two identical wires of rubber and iron are stretched by the same weight, then the number of atoms in the iron wire will be

(a) Equal to that of rubber (b) Less than that of the rubber (c) More than that of the rubber (d) None of the above Answer-c (7)

146.Two uniform similar discs roll down two inclined planes of length S and 2S respectively as shown is the fig. The velocities of two discs at the points A and B of the inclined planes are related as

(a) v1 = v2 (b) v1 =2v2 (c) v1 = v1 (v2/4) (d) v1 =( 3/4) v2 Ans. a (59)

The escape velocity for the earth is 11.2 km/sec. The mass of another planet is 100 times that of the earth and its radius is 4 times that of the earth. The escape velocity for this planet will be

(a) 112.0 km/s (b) 5.6 km/ (c) 280.0 km/s (d) 56.0 km/s Answer: d (8)

36. If a load of 9 kg is suspended on a wire, the increase in length is 4.5 mm. The force constant of the wire is

(a) 0.49×104 N/m (b) 1.96×104 N/m (c) 4.9×104 N/m (d) 0.196×104 N/m Answer-b (16)

The escape velocity of an object on a planet whose g value is 9 times on earth and whose radius is 4 times that of earth in km/s is

(a) 67.2 (b) 33.6 (c) 16.8 …

44. After effects of elasticity are maximum for

(a) Glass (b) Quartz (c) Rubber (d) Metal Answer-a (17)

43. The elasticity of invar

(a) Increases with temperature rise (b) Decreases with temperature rise (c) Does not depend on temperature (d) None of the above Answer-c (47)

42. The force constant of a wire does not depend on

(a) Nature of the material (b) Radius of the wire (c) Length of the wire (d) None of the above Answer-d (7)

37. The escape velocity of a planet having mass 6 times and radius 2 times as that of earth is

(a) √3 ve (b) 3 ve (c) √2 ve (d) 2 ve Answer: a (6)

39. A steel wire is stretched with a definite load. If the Young’s modulus of the wire is Y. For decreasing the value of Y

(a) Radius is to be decreased (b) Radius is to be increased (c) Length is to be increased (d) None of the above ANSWER-D (11)

35. A weight of 200 kg is suspended by vertical wire of length 600.5 cm. The area of cross-section of wire is 1mm2. When the load is removed, the wire contracts by 0.5 cm. The Young’s modulus of the material of wire will be

(a) 2.35×1012 N/m2 (b) 1.35×1010 N/m2 (c) 13.5×1011 N/m2 (d) 23.5×109 N/m2 Answer- (8)

144. A ring of radius 4a is rigidly fixed in vertical position on a table. A small disc of mass m and radius a is released as shown in the fig. When the disc rolls down, without slipping, to the lowest point of the ring, then its speed will be

(a) √ga (b) √2ga (c) √3ga (d) √4ga Ans. d (133)

34. Two wires of copper having the length in the ratio 4 : 1 and their radii ratio as 1 : 4 are stretched by the same force. The ratio of longitudinal strain in the two will be

(a) 1 : 16 (b) 16 : 1 (c) 1 : 64 (d) 64 : 1 Answer-b (2)

The escape velocity from the surface of earth is Ve . The escape velocity from the surface of a planet whose mass and radius are 3 times those of the earth will be

(a) Ve (b) 3 Ve (c) 9 Ve (d) 27 Ve Answer: a (4)

The mass of the earth is 81 times that of the moon and the radius of the earth is 3.5 times that of the moon. The ratio of the escape velocity on the surface of earth to that on the surface of moon will be

(a) 0.2 (b) 2.57 (c) 4.81 (d) 0.39 Answer: c (2)

142. A solid ball of mass m and radius r rolls without slipping along the track shown in the fig. The radius of the circular part of the track is R. The ball starts rolling down the track from rest from a height of 8R from the ground level. When the ball reaches the point P then its velocity will be

(a) √(gR) (b) √(5gR) (c) √(10gR) (d) √(3gR) Ans. c (21)

Escape velocity on a planet is ve . If radius of the planet remains same and mass becomes 4 times, the escape velocity becomes

(a) 4 ve (b) 2 ve (c) ve …

The escape velocity of an object from the earth depends upon the mass of the earth (M), its mean density (p), its radius (R) and the gravitational constant (G). Thus the formula for escape velocity is

Answer: a (5)

A missile is launched with a velocity less than the escape velocity. The sum of its kinetic and potential energy is

(a) Positive (b) Negative (c) Zero (d) May be positive or negative depending upon its initial velocity Answer: b (8)

138. The acceleration of a body rolling down on an inclined plane does not depend upon

(a) Angle of inclination of the plane (b) Length of plane (c) Acceleration due to gravity of earth (d) Radius of gyration of body Ans. b (5)

If g is the acceleration due to gravity at the earth’s surface and r is the radius of the earth, the escape velocity for the body to escape out of earth’s gravitational field is

(a) gr (b) √2gr (c) g/r (d) r/g Answer: b (4)

136. A disc of radius R is rolling down an inclined plane whose angle of inclination is θ , Its acceleration would be

(a) 5/7 g sinθ (b) 2/3 g sinθ (c) 1/2 g sinθ (d) 3/5 g sinθ Ans. b (16)

135. A cylinder of mass M and radius R rolls on an inclined plane. The gain in kinetic energy is

(a) (1/2)Mv2 (b) (1/2) (c) (3/4)Mv2 (d) (3/4)Iω2 Ans. c (15)

The escape velocity for a rocket from earth is 11.2 km/sec. Its value on a planet where acceleration due to gravity is double that on the earth and diameter of the planet is twice that of earth will be in km/sec

(a) 11.2 (b) 5.6 (c) 22.4 (d) 53.6 Answer: c (6)

The escape velocity from the earth is about 11 km/second. The escape velocity from a planet having twice the radius and the same mean density as the earth, is

(a) 22 km/sec (b) 11 km/s (c) 5.5 km/sec (d) 15.5 km/sec Answer: a (6)

134. A solid cylinder 30 cm in diameter at the top of an inclined plane 2.0 m high is released and rolls down the incline without loss of energy due to friction. Its linear speed at the bottom is

(a) 5.29 m/sec (b) 4.1 × 103 m/sec (c) 51 m/sec (d) 51 cm/sec Ans. a (62)

The moment of inertia of a solid cylinder about its axis is I. It is allowed to roll down an incline without slipping. If its angular velocity at the bottom be ω , then K.E. of the cylinder will be

(a) Iω2 (b) (3/2) Iω2 (c) 2Iω2 (d) (1/2)Iω2 Ans. b (47)

140. A ring is rolling on an inclined plane. The ratio of the linear and rotational kinetic energies will be

(a) 2 : 1 (b) 1 : 2 (c) 1 : 1 (d) 4 : 1 Ans. c (12)

For the moon to cease to remain the earth’s satellite, its orbital velocity has to increase by a factor of

(a) 2 (b) √ 2 (c) 1/√2 (d) √3 Answer: b (7)

139. A ring, a solid sphere, a disc and a solid cylinder of same radii roll down an inclined plane, which would reach the bottom in the last

(a) Ring (b) Disc (c) Solid sphere (d) Solid cylinder Ans. a (43)

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