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1. There are two objects of masses 1 kg and 2 kg located at (1, 2) and (-1, 3) respectively. The coordinates of the centre of mass are
A. A
B. B
C. C
D. D
2. The motion of a potter's wheel is an example of
A. rolling motion
B. rotatory motion
C. translatory motion
D. precessional motion
3. The general motion of a rigid body consists of
A. translational motion only
B. rotational motion only
C. both, translational and rotational motion
D. does not include translational and rotational motions
4. A rigid body is one
A. the sum of distances of all particles from the axis remains constant
B. in which the distance between all pairs of particles remains fixed.
C. whose centre of mass follows a parabolic path
D. that deforms and comes back to its original shape after getting deformed
5. If a shell at rest explodes, then, the centre of mass of the fragments
A. remains at rest.
B. Moves along a parabolic path.
C. Moves along a straight line.
D. moves along an elliptical path.
6. A child sits stationary at one end of long trolley moving uniformly with speed v on a smooth horizontal floor. If the child gets up and runs about on the trolley in the forward direction with speed u. The centre of mass of the system (child + trolley) will move with speed
A. v
B. zero
C. u + v
D. v / u
9. The centre of mass of a body is located
A. outside the system
B. inside or outside the system
C. inside the system
D. at the centre of system
10. When a shell was following a parabolic path in the air, it explodes somewhere in its flight. The centre of mass of fragments will continue to move in
A. any direction
B. horizontal direction
C. same parabolic path.
D. vertical direction
11. If the resultant of all external forces is zero, then velocity of centre of mass will be
A. maximum
B. zero
C. constant
D. minimum
12. Every point in a rotating rigid body has the same __________at any instant of time.
A. linear velocity
B. angular velocity
C. displacement
D. linear momentum
14. The centre of mass of a system of particles does not depend on
A. masses of the particles
B. forces on the particles.
C. relative distances between the particles.
D. position of the particles.
15. If the net force acting on the system of particles is zero, then which of the following may vary
A. moment of inertia
B. Kinetic energy of the system
C. velocity of centre of mass
D. position of centre of mass
16. If three balls of same radius are placed touching each other on a horizontal surface such that they will form an equilateral triangle, when their centers are joined. What will be the position of the centre of mass of the system?
A. At the point of intersection of the medians.
B. At the line joining the centers of any two balls.
C. At the centre of one of the ball.
D. At the horizontal surface.
17. When external forces acting on a body are zero, then its centre of mass
A. remains stationary
B. moves with uniform velocity
C. either remains stationary or moves with uniform velocity
D. none of these
18. Two blocks of the masses 10 kg and 4 kg are connected by a spring of negligible mass and placed on a frictionless horizontal surface. An impulse gives a velocity of 14 m/s to the heavier block. The velocity of centre of mass is
A. 10 m/s
B. 5 m/s
C. 5 m/s
D. 20 m/s
19. The sum of moments of masses of all the particles in a system about the centre of mass is always:
A. maximum
B. zero
C. infinite
D. minimum
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