Centre of Mass of Discrete Particles
Which of the following statements are correct?
(1) Centre of mass of a body always coincides with the centre of gravity of the body. (2) Centre of mass of a body is the point at which the total gravitational torque on the body is zero. (3) A couple on a body produces both translational and rotational motion in a body (4) Mechanical advantage greater than one means that small effort can be used to lift a large load.
Show answer and solution
Answer: (d)
- (1) False: CM and centre of gravity coincide only when is uniform over the body.
- (2) Taken as correct: in uniform the gravitational torque about the CM is zero.
- (3) False: a couple gives zero net force, so it produces only rotation.
- (4) True: means a small effort lifts a large load.
- So the answer is (d) (2) and (4).