10 QA on centre of mass | Learn Physics

 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)