Question

A disc of mass 2kg and diameter 2m is performing rotational motion. Find the work done, if the disc is rotating from 300rpm to 600rpm.

• A. 1479 J
• B. 147.9 J
• C. 14.79 J
• D. 1.479 J

Answer 1

Answer: (A)

1479 J

Answer 2

The correct option is A) 1480 J
I = $\frac{mR^2}{2} = 1 kg/m^2$

$ω_i = \frac{300 \times 2π}{60} = 10π$

$ω_f = \frac{600 \times2π} {60} = 20π$

△KE = $\frac{1}{2} I(ω_f)^2 - \frac{1}{2}(Iω_i)^2$

= $\frac{1}{2}((20π)^2 - (10π)^2)$

$2 \times300π^2= 1480 J$