Question

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 rotation motion in a body.
d) Mechanical advantage greater than one means that small effort can be used to lift a large load.

• A. (a) and (b)
• B. (b) and (c)
• C. (c) and (d)
• D. (b) and (d)

Answer 1

The correct option is D (b) and (d)

Centre of mass may lie on centre of gravity but net torque of gravitational pull is zero about centre of mass.

Mechanical advantage = $\frac{\text{Load}}{\text{Effort}}$ > 1
$\Rightarrow$ Load > Effort