Question

Two bodies of 2 Kg & 4 Kg are moving with velocities 20 m/s and 10 m/s respectively

towards each other under mutual gravitational attraction. Find the velocity of their centre of

mass in m/s.

(A) 5 (B) 6 (C) 8 (D) Zero

Answer 1

The velocity of their centre of  mass is zero.

Explanation:

We are given

m1 =2 kg , m2=4 kg

u1=20 m/s , u2 = 10 m/s

v=?m/s

• We know if two bodies are moving opposite to each other then they start moving with a common velocity v.

• VCM = m1.v1 + m2.v2 / m1 + m2

2(20)-4(10)=(2+4)v

40-40=6 v

0=6 v

v=0/6

v=0 m/s

Due to no change in centre of mass, internal force does not change the position of centre of mass.

VCM = Zero

Hence the velocity of their centre of  mass is zero.

Also learn more

The velocity of a particle moving with constant

acceleration at an instant t, is 10m/s. After 5 seconds  of that instant the velocity of the particle is 20m/s. The velocity at 3 second before to is?

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Answer 2

Explanation:

these is the answer

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