Q. Which of the following statements are correct ? (a) Centre of mass of a body always coincides with the centre of gravity of the body. (b) Centre of mass of a body is the point at which the total gravitational torque on the body is zero. (c) A couple on a body produce both translational and rotational motion in a body. (d) Mechanical advantage greater than one means that small effort can be used to lift a large load.
A) (b) and (d)
B) (a) and (b)
C) (b) and (c)
D) (c) and (d)
Explanation
[Solution] (d) is correct. (a) is false for non-uniform g, and (c) is false since a couple causes only rotation. The official key takes (b) as correct (in a uniform field the gravitational torque about the centre of mass is zero), giving (b) and (d). Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.