Question

The angular velocity of a body is $\overset{\rightarrow}{\omega} = 2\widehat{i} + 3\widehat{j} + 4\widehat{k}$ and a torque $\overset{\rightarrow}{\tau} = \widehat{i} + 2\widehat{j} + 3\widehat{k}$ acts on it. The rotational power will be

• A. 20 W
• B. 15 W
• C. $\sqrt{17}$W
• D. $\sqrt{14}$W

Answer 1

Answer: (A)

20 W

Answer 2

Power $(P) = \overset{\rightarrow}{\tau}.\overset{\rightarrow}{\omega} = (i + 2\widehat{j} + 3\widehat{k}).(2\widehat{i} + 3\widehat{j} + 4\widehat{k})$

$= 2 + 6 + 12$= 20 W