Friday, 28 October 2016

5 Circular motion MCQs with answers

Circular motion is 5th chapter of FSC part 1 from Physics book with centripetal motion and rotational torque and momentum as important topics.

Circular motion MCQs

1.           A point mass moves along the circumference of a circle of radius R. As it completes 4 rotations, its displacement and distance covered are
(a) 0 and 8 R                            (b) 8 R and 0
(c) 8 R and 2 R                         (d) none of these

(a) 30o                                      (b) 60o
(c) 90o                                      (d) 180o

3.           1 rad equals
(a) 53.7o                                   (b) 35.7o
(c) 57.3o                                   (d) 75.3o

4.           The dimensions of angular displacement are
(a) [L]                                       (b) [Lo]
(c) [L2]                                      (d) [L-]

5.           The circumference of a circle subtends at the centre an angle equal to

2

6.           A flywheel makes 300 rpm. Its angular velocity in rad s- is
(a) 10                                       (b) 20
(c) 30                                     (d) none of these

7.           The dimensions of angular velocity are
(a) [LT]                                     (b) [LT-]
(c) [T]                                      (d) [T-]

8.           The angular speed of a minute hand in a clock in rad s-1 is
(a) 5.8×10-                             (b) 1.7×10-
(c) 5.2 × 10-                           (d) 1.0 × 10-

9.           The linear speed of a point on the rim of a wheel of diameter
1 m which makes 30 rpm is
(a)  ms-1                                   (b)  ms-1
(c) 30 ms-1                               (d) 60 ms-1

10.        The ratio of the angular speed of the minute hand to the hour hand of a clock is
(a) 1 : 6                                    (b) 6 : 1
(c) 1 : 12                                  (d) 12 : 1

11.        All points of a rigid body rotating about a given axis have the same
(a) tangential velocity              (b) angular velocity
(c) tangential acceleration        (d) angular acceleration

12.        The centripetal force acting on a body of mass m moving in a circle of radius r with constant angular speed is
(a) FC = mr                              (b) FC = m2r
(c) FC = mr 2                                               (d) FC = m2r2

13.        A satellite circles the Earth with a speed v at a distance r from the centre of Earth. Increasing the speed twice will make the satellite move in a circle of radius
(a) 2 r                                       (b) r/4
(c) 4 r                                      (d) r/2

14.        When a stone is whirled in a vertical circle by a string, the tension in the string is maximum at the
(a) centre                                  (b)top
(c) bottom                                (d) neither of these points

15.        Moment of inertia has the dimensions
(a) [MLT]                                   (b) [ML2T-2 ]
(c) [ML2]                                    (d) [ML2T-1]

16.        Rotational analogue of force is
(a) angular momentum             (b) moment of inertia
(c) moment of force                 (d) torque

17.        The moment of inertia of a body depends upon
(a)         mass of a body and its size
(b)         its angular momentum
(c)         mass of a body and its angular speed
(d)        mass as well as its distribution about the axis of rotation.

18.        The angular momentum L is given by
(a) m                                         (b)  × r
(c) r × F                                    (d) r × p

19.        Rate of change of angular momentum is equal to
(a) force                                   (b) impulse
(c) torque                                 (d) inertia

20.        In the absence of any external torque, a decrease in the moment of inertia results in an increase in the angular velocity such that
(a) I2 constant  (b) Iconstant  (c) I constant   (d) I2constant 21.        If Earth shrinks half of its present size, its new angular velocity of rotation about its axis of rotation becomes
(a) twice                                   (b) three times
(c) four times                           (d) six times

22.        If a steel ball of mass m and radius r is moving with angular velocity , its rotational kinetic energy is
(a) mr                                        (b) 1 m2 r (c) mr2                                  (d) m2 r2

23.        The weight of a man in an elevator descending with an acceleration of 4.9 ms- will become
(a) twice                                    (b) half
(c) zero                                    (d) unchanged

24.        An astronaut of mass 100 kg is orbiting in a spaceship at an
R      -2, his altitude h =  (R = radius of Earth). Taking g = 10 ms 2
weight inside the spaceship is
(a) 500 N                                  (b) 250 N
(c) 125 N                                   (d) 0 N

25.        The rotational kinetic energy of a hoop of mass m moving down an inclined plane with velocity v will be
(a) 1 mv2                                  (b) 1 mv2
(c) mv2                                  (d) mv2

26.        The linear velocity of a disc moving down an inclined plane is
4gh (a) gh                                       (b) 3
2gh      gh (c)     (d)
3                                             2

27.        The physical quantity which produces angular acceleration in a body is called
(a) angular velocity                  (b) momentum
(c) centripetal force                  (d) torque

28.        The rate of change of angular momentum of a body is called
(a) applied torque                    (b) force
(c) impulse                               (d) moment of force

29.        Angular momentum of a body under the central force is
(a) zero                                     (b) maximum
(c) minimum                           (d) constant

30.        The number of geostationary satellites required for global TV transmission  is
(a) 2                                          (b) 3
(c) 4                                          (d) 6

31.        A geostationary satellite completes one revolution around the
Earth in
(a) 6 hr                                     (b) 12 hr
(c) 18 hr                                   (d) 24 hr

32.        Moment of inertia of a solid sphere of mass M and radius R about an axis passing through its centre is
(a) MR                                    (b) MR2
(c) MR2                                      (d) MR2
33.        A body of mass m moves with angular velocity  in a circle of radius r about point O. If moment of inertia of the body about O is I and v is its linear speed, then its angular momentum about
O  is
(a) Iv                                          (b) I
(c) mv2r                                      (d) mr2

34.        Finite angular displacement of a rotating body is taken as
(a) vectors                               (b) scalars
(c) neither scalars nor vectors  (d) both scalars as well as vectors.

Answer of Chapter 5

 1 a 21 c 2 d 22 b 3 c 23 c 4 b 24 d 5 b 25 c 6 a 26 b 7 d 27 d 8 b 28 b 9 b 29 b 10 d 30 b 11 c 31 b 12 b 32 d 13 a 33 a 14 b 34 d 15 b 35 a 16 c 36 b 17 c 37 d 18 d 38 b 19 d 39 b 20 d 40 b