Question

When a ceiling fan is switched off, its velocity falls to half in 36 rotations. How many more rotations it will make?

• A. 36
• B. 24
• C. 18
• D. 12

Answer 1

Answer: (D)

12

Answer 2

ω² = ω₀² – 2αθ or ω₀² - $\left( \frac{\omega_{0}}{2} \right)^{2}$ = 2 αθ

or $\frac{3\omega_{0}^{2}}{4}$ = 2α(36 rot). ….. ….. (i)

$\frac{\omega_{0}^{2}}{4}$ = 2 α(x rot) ……….. (ii)

Solving (i) and (ii) x = 12