May, 2022Flame Institute

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 …

2. Assertion : If the net external force on the body is zero, then its acceleration is zero. Reason : Acceleration does not depend on force.

3. Assertion : Newton’s second law of motion gives the measurement of force. Reason : According to Newton’s second law of motion, force is directly proportional to the rate of change of momentum.

The gravitational force between two stones of mass 1 kg each separated by a distance of 1 metre in vacuum is

(a) Zero (b) 6.675×10-5 newton (c) 6.675×10-11 newton (d) 6.675×10-8 newton Answer: c (8)

7. Which of the following is the evidence to show that there must be a force acting on earth and directed towards the sun

(a) Deviation of the falling bodies towards east (b) Revolution of the earth round the sun (c) Phenomenon of day and night (d) Apparent motion of sun round the earth Answer: b (4)

The atmosphere is held to the earth by

(a) Winds (b) Gravity (c) Clouds (d) None of the above Answer: b (7)

A satellite of the earth is revolving in a circular orbit with a uniform speed v. If the gravitational force suddenly disappears, the satellite will

(a) Continue to move with velocity v along the original orbit (b) Move with a velocity v, tangentially to the original orbit (c) Fall down with increasing velocity (d) Ultimately come to rest somewhere on the original orbit Answer: b …

11. Figures I, II, III and IV depict variation of force with time

Ans. c (10)

6. If the distance between two masses is doubled, the gravitational attraction between them

(a) Is doubled (b) Becomes four times (c) Is reduced to half (d) Is reduced to a quarter Answer: d (10)

10. The variation of momentum with time of one of the body in a two body collision is shown in fig. The instantaneous force is maximum corresponding to point

(a) P (b) Q (c) R (d) S Ans. c (11)

8. A particle of mass m, initially at rest, is acted upon by a variable force F for a brief interval of time T. It begins to move with a velocity u after the force stops acting. F is shown in the graph as a function of time. The curve is a semicircle.

Ans. c (37)

47. Four particles each of mass m are placed at the corners of a square of side length l. The radius of gyration of the system about an axis perpendicular to the square and passing through its centre is

(a) l/ √2 (b) l/2 (c) l (d) (√2)l Ans. a (28)

48. The moment of inertia of a rod (length l, mass m) about an axis perpendicular to the length of the rod and passing through a point equidistant from its mid point and one end is

(a) ml2/12 (b) 7/48 ml2 (c) 13 ml2 (d) 19/48ml2 Ans. b (5)

6. Which of the following graph depicts spring constant k versus length l of the spring correctly

Ans. d (5)

7. A particle of mass m moving with velocity u makes an elastic one dimensional collision with a stationary particle of mass m. They are in contact for a very short time T. Their force of interaction increases from zero to F0 linearly in time T/2, and decreases linearly to zero in further time T/2. The magnitude of F0 is

(a) mu/T (b) 2mu / T (c) mu/ 2T (d) None of these ANS. b (5)

46. A wheel of mass 10 kg has a moment of inertia of 160 kg–m2 about its own axis, the radius of gyration will be

(a) 10 m (b) 8 m (c) 6 m (d) 4 m Ans. d (42)

45. Moment of inertia of a disc about its own axis is I. Its moment of inertia about a tangential axis in its plane is

(a) 5/2I (b) 3 I (c) 3/2 I (d) 2 I Ans. a (8)

Assertion : Soft steel can be made red hot by continued hammering on it, but hard steel cannot. Reason : Energy transfer in case of soft iron is large as in hard steel.

5. A body of 2 kg has an initial speed 5ms–1. A force acts on it for some time in the direction of motion. The force time graph is shown in figure. The final speed of the body.

Ans. c (9)

Assertion : Mountain roads rarely go straight up the slope. Reason : Slope of mountains are large therefore more chances of vehicle to slip from roads.

44. The moment of inertia of semicircular ring about its centre is

(a) MR2 (b) MR2/2 (c) MR2/4 (d) None of these Ans. a (7)

4. Figure shows the displacement of a particle going along the X-axis as a function of time. The force acting on the particle is zero in the region

(a) AB (b) BC (c) CD (d) DE ANS. a, c (22)

Assertion : A work done in moving a body over a closed loop is zero for every force in nature. Reason : Work done does not depend on nature of force.

43. A circular disc is to be made by using iron and aluminium, so that it acquires maximum moment of inertia about its geometrical axis. It is possible with

(a) Iron and aluminium layers in alternate order (b) Aluminium at interior and iron surrounding it (c) Iron at interior and aluminium surrounding it (d) Either (a) or (c) Ans. b (3)