Question

The velocities of three particles of masses 10 kg, 20 kg and 30 kg are 10i, 10j and 10k m/s, respectively. What is the velocity of their centre of mass?

(a) (i + 2j + 3k) m/s

(b) 10 (i + j + k) m/s

(c) (10i + 20j + 30k) m/s

(d) (3i + 2j + k) m/s

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This interesting question is from System of Particles topic in section System of Particles and Rotational Motion of Physics – Class 11

Answer 1

The correct choice is (a) (i + 2j + 3k) m/s

To elaborate: The velocity of the centre of mass = (m1*v1 + m2*v2 + m3*v3)/(m1 + m2 + m3)

 = (10*10i + 20*10j + 30*10k) / (10 + 20 + 30)

 = (100i + 200j + 300k) / 100

 = (i + 2j + 3k) m/s.