10 Question- Answer on centre of mass
1. The unit of position vector of centre of mass is
(a) Metre
(b) Kg
(c) Kg-m2
(d) Kg-m
Ans(a)
2. Two particles of masses m1 and m2 (m1> m2) attract each other with a force inversely proportional to the square of the distance between them. If the particles are initially held at rest and then released, the centre og mass will
(a) Move towards m1
(b) Move towards m2
(c) Remain at rest
(d) Nothing can be said
Ans: (c)
3. A system consists of three particles, each of mass m and located at (1, 1), (2, 2) and (3, 3) .The co-ordinates of the centre of mass are?
(a) (1, 1)
(b) (2, 2)
(c) 3, 3)
(d) (6, 6)
Ans: (b)
4. Consider a system of two identical particles. One of the particles has an acceleration a, while the other is at rest. The centre of mass has an acc. Of :
(a) 2a
(b) Zero
(c) 0.5a
(d) A
Ans: (c )
5. Two particles A and B initially at rest move towards each other under a mutual force of attraction. At the instant when velocity of A is v and that of B is 2 v, the velocity of centre of mass of the system is :
(a) V
(b) 2v
(c) 3v
(d) Zero
Ans: (d)
6. The motion of centre of mass depends on
(a) Total external forces
(b) Total internal forces
(c) Sum of (a) and (b)
(d) None of these
Ans: ( a)
7. The centre of mass of a rigid body lies
(a) Inside the body
(b) Outside the body
(c) On its surface
(d) Anyone of these
Ans : ( d)
8. A shell at rest explodes. The centre of mass of the fragments
(a) Moves along a parabolic path
(b) Moves along st. line
(c) Moves along an elliptical path
(d) Remains at rest
Ans: ( d)
9. The sum of moments of masses of all particles in a system about the centre of mass is always
(a) Maximum
(b) Minimum
(c) Infinite
(d) Zero
Ans: ( d)
10. The centre of mass of two particles lies on the line
(a) Joining the particle
(b) Perpendicular to the line joining the particles
(c) At any angle to this line
(d) Nothing can be said
Ans: (a)