PhysicsFlame Institute

Earth is revolving around the sun if the distance of the Earth from the Sun is reduced to 1/4th of the present distance then the present day length reduced by

(a) 1/4 (b) 1/2 (c) 1/8 …

112. According to Hook’s law force is proportional to

(a) 1/x (b) 1/x2 (c) x (d) x2 Answer-c (7)

111. A rubber cord catapult has cross-sectional area

A rubber cord catapult has cross-sectional area 25mm2 and initial length of rubber cord is It is stretched to and then released to project a missile of mass (Taking YRUBBER=5×108N/m2) velocity of projected missile is (a) 20 m/s …

108. Two wires A and B are of same materials. Their lengths are in the ratio 1 : 2 and diameters are in the ratio 2 : 1 w

Two wires A and B are of same materials. Their lengths are in the ratio 1 : 2 and diameters are in the ratio 2 : 1 when stretched by force FA and FB respectively they get equal increase in …

The condition for a uniform spherical mass m of radius r to be a black hole is [G= gravitational constant and g= acceleration due to gravity]

(a) (2Gm/r)1/2≤c (b) (2Gm/r)1/2=c (c) (2Gm/r)1/2≥c (d) (gm/r)1/2≥c Answer: c (4)

Two satellite are revolving around the earth with velocities

Two satellite are revolving around the earth with velocities v1 and v2 and in radii r1 and r2 (r1 > r2) respectively Then (a) v1 = v2 …

110. The area of cross section of a steel wire

The area of cross section of a steel wire (Y=2.0×1011 N/m2) is 0.1 cm2 . The force required to double its length will be (a) 2×1012 N/m …

109. The breaking stress of a wire depends upon

(a) Length of the wire (b) Radius of the wire (c) Material of the wire (d) Shape of the cross section Answer-c (13)

Hubble’s law states that the velocity with which milky way is moving away from the earth is proportional to

(a) Square of the distance of the milky way from the earth (b) Distance of milky way from the earth (c) Mass of the milky way (d) Product of the mass of the milky way and its distance from the …

If orbital velocity of planet is given by

If orbital velocity of planet is given by v =Ga Mb Rc , then (a) a=1/3,b=1/3,c=-1/3 (b) a=1/2,b=1/2,c=-1/2 (c) a=1/2,b=-1/2,c=-1/2 (d) a=1/2,b=-1/2,c=-1/2 Answer: b (8)

The mass of a planet that has a moon whose time period and orbital radius are T and R respectively can be written as

(a) 4π2 R3 G-1T-2 (b) 8π2 R3 G-1T-2 (c) 12π2 R3 G-1T-2 (d) 16π2 R3 G-1T-2 Answer: a (10)

The eccentricity of earth’s orbit is 0.0167. The ratio of its maximum speed in its orbit to its minimum speed is

(a) 2.507 (b) 1.033 (c) 8.324 (d) 1.000 Answer: b (7)

28. Two circular discs A and B are of equal masses and thickness but made of metals with densities

Two circular discs A and B are of equal masses and thickness but made of metals with densities dA and dB (dA>dB) . If their moments of inertia about an axis passing through centres and normal to the circular faces …

27. The moment of inertia of a solid sphere of density

The moment of inertia of a solid sphere of density ρ and radius R about its diameter is (a) (105/176)R5ρ (b) (105/176)R2ρ (c) (176/105)R5ρ (d) (176/105)R2ρ Ans. c (10)

The period of moon’s rotation around the earth is nearly 29 days. If moon’s mass were 2 fold, its present value and all other things remained unchanged, the period of moon’s rotation would be nearly

(a) 29√2 days (b) 29 /√2 days (c) 29 × 2 days (d) 29 days Answer: d (4)

A body revolved around the sun 27 times faster then the earth what is the ratio of their radii

(a) 1/3 (b) 1/9 (c) 1/27 (d) 1/4 Answer; b (3)

The maximum and minimum distances of a comet from the sun are

The maximum and minimum distances of a comet from the sun are 8 × 1012 m and 1.6 × 1012 m . If its velocity when nearest to the sun is 60 m/s, what will be its velocity in m/s …

15. Mark the wrong statement

(a) Sliding of molecular layer is much easier than compression or expansion (b) Reciprocal of bulk modulus of elasticity is called compressibility (c) It is difficult to twist a long rod as compared to small rod (d) Hollow shaft is …

48. The angular velocity of a body is

The angular velocity of a body is →w= 2^j+3^k+4^k and a torque →τ = ^j+2^k+3^k acts on it. The rotational power will be (a) 20 W (b) 15 W (c) √17 W (d) √17 W Ans. a (8)

47. A ring, a solid sphere and a thin disc of different masses rotate with the same kinetic energy. Equal torques are applied to stop them. Which will make the least number of rotations before coming to rest

(a) Disc (b) Ring (c) Solid sphere (d) All will make same number of rotations Ans. d (15)

46. If the angular momentum of a rotating body is increased by 200%, then its kinetic energy of rotation will be increased by

(a) 400% (b) 800% (c) 200% (d) 100% Ans. b (13)

18. Shearing stress causes change in

(a) Length (b) Breadth (c) Shape (d) Volume Answer-c (5)

45. A wheel is rotating with an angular speed of 20 rad/s . It is stopped to rest by applying a constant torque in 4s

A wheel is rotating with an angular speed of 20 rad/s . It is stopped to rest by applying a constant torque in 4s . If the moment of inertia of the wheel about its axis is 0.20 kg-m2, then …

17.A rod of length l and radius r is joined to a rod of length l/2 and radius r/2 of same material. The free end of small rod is

A rod of length l and radius r is joined to a rod of length l/2 and radius r/2 of same material. The free end of small rod is fixed to a rigid base and the free end of larger …

44. A disc and a ring of same mass are rolling and if their kinetic energies are equal, then the ratio of their velocities will be

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

16. A 2 m long rod of radius 1 cm which is fixed from one end is given a twist of 0.8 radians. The shear strain developed will be

(a) 0.002 (b) 0.004 (c) 0.008 (d) 0.016 Answer-b (22)

In the solar system, which is conserved

(a) Total Energy (b) K.E. (c) Angular Velocity (d) Linear Momentum Answer: a (9)

What does not change in the field of central force

(a) Potential energy (b) Kinetic energ (c) Linear momentum (d) Angular momentum Answer:D (10)

Suppose the law of gravitational attraction suddenly changes and becomes an inverse cube law i.e F∞1/r3 . , but still remaining a central force. Then

(a) Keplers law of areas still holds (b) Keplers law of period still holds (c) Keplers law of areas and period still hold (d) Neither the law of areas, nor the law of period still holds Answer: d (14)