Question

The angular speed of rotating rigid body is increased from 4 w to 5 w. The percentage increase in its K.E. is –

• A. 20 %
• B. 25 %
• C. 125 %
• D. 56 %

Answer 1

Answer: (D)

56 %

Answer 2

K.E. = $\frac{1}{2}I\omega^{2}$Ž K.E. ∝ w² % increase K.E.

= $\frac{KE_{f}–KE_{i}}{KE_{i}}$ × 100

= $\frac{5^{2}–4^{2}}{4^{2}} \times 100$

= $\frac{9}{16} \times 100$ = 56%