Question

A man, sitting firmly over a rotating stool has his arms stretched. If he folds his arms, the work done by the man is :

• A. zero
• B. positive
• C. negative
• D. may be positive or negative

Answer 1

The correct option is B positive

When the arms are stretched the rotational inertia is higher. When the man folds his arm he is basically decreasing his rotational inertia thereby gaining more angular velocity using the principle of conservation of angular momentum. This implies more angular distance is covered in the same time giving us positive work.