Which statements are correct? (I) Centre of mass always coincides with centre of gravity. (II) The centre of mass is the point where total gravitational torque on a body is zero. (III) A couple causes both translation and rotation. (IV) Mechanical advantage >1 lets a small effort lift a large load.
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Question

Which statements are correct? (I) Centre of mass always coincides with centre of gravity. (II) The centre of mass is the point where total gravitational torque on a body is zero. (III) A couple causes both translation and rotation. (IV) Mechanical advantage >1 lets a small effort lift a large load.

Options

G1 Physics · Accepted Answer

Step 1: For a uniform gravitational field, the resultant weight produces zero torque about the centre of mass, so II is taken as true in the source. Step 2: A force couple has zero resultant force, causing rotation but not translation, so III is false. Step 3: IV is true by definition of mechanical advantage. Step 4: I need not hold for nonuniform gravity. Step 5: Correct IIs and IV. Final answer: A — (II) and (IV).