Question

A gymnast on ice folds his arms while rotation. Which of the following statements is true?

• A. Speed of rotation increases as friction decreases
• B. Rotational kinetic energy decreases because moment of inertia decreases
• C. Rotational kinetic energy increases as angular momentum remains conserved
• D. None of the above

Answer 1

The correct option is C Rotational kinetic energy increases as angular momentum remains conserved

$K.E.=\frac{L^2}{2I}$
$L$ remains constant and due to folding of arms $I$ decreases & K.E. increases.