Question

Particles of masses 1 kg and 3 kg are at (2i+5j+13k) m and (-6i+4j-2k) m. What is the position of their centre of mass?

(a) 1/4 (-16i + 17j + 7k) m

(b) 1/4 (-8i + 17j + 7k) m

(c) 1/4 (-6i + 17j + 7k) m

(d) 1/4 (-6i + 17j + 5k) m

I had been asked this question in semester exam.

I need to ask this question from System of Particles in chapter System of Particles and Rotational Motion of Physics – Class 11

Answer 1

Correct answer is (a) 1/4 (-16i + 17j + 7k) m

For explanation: Sum of masses = 1 + 3 = 4

x-coordinate;

(1*2-3*6)/4 = -16/4

y-coordinate;

(1*5 + 3*4)/4 = 17/4

z-coordinate;

(1*13-3*2)/4 = 7/4

Position of centre of mass = 1/4 (-6i + 17j + 5k) m.