Question

For an object with the centre of mass at the origin, the x-coordinates of particles of the object _____

(a) may be all positive

(b) may be all negative

(c) may be all non-negative

(d) cannot be predicted

This question was addressed to me at a job interview.

The origin of the question is System of Particles topic in portion System of Particles and Rotational Motion of Physics – Class 11

Answer 1

Correct option is (c) may be all non-negative

Easiest explanation: For an object to have the x-coordinate of its centre of mass, there should be particles on both the negative and positive coordinates of the plane for the sum to be zero. However, for 1-dimensional particles that all lie on the y-axis symmetric about the x-axis, the x-coordinate is zero – which is neither positive nor negative, i.e., non-negative.