Physics · SYSTEMS OF PARTICLES AND ROTATIONAL MOTION

Consider the following statements regarding the Centre of Gravity (CG) and Centre of Mass (CM) of an extended body: (A) The centre of gravity is defined as the point where the total gravitational torque on the body is zero. (B) The centre of gravity of a body always coincides with its centre of mass, even in a non-uniform gravitational field. (C) For an irregular body suspended by a string, the vertical line passing through the point of suspension passes through the centre of gravity. (D) When a cardboard balances horizontally on the tip of a pencil, the normal reaction of the tip balances the total weight and exerts zero net torque about the CG. How many of the above statements are correct?

1. A
   Only one
2. B
   Only two
3. C
   Only three
4. D
   All four