Question

Magnitude of angular momentum of a wheel changes from $2L$ to 3 $L$ in 5 sec. by a constant torque acting opposite to initial direction of rotation. What is the magnitude of the torque?

• A. $\frac{L}{5}$
• B. $L$
• C. $\frac{2L}{5}$
• D. $\frac{3L}{5}$

Answer 1

The correct option is A $\frac{L}{5}$

$\begin{array}{c}\text{Given - Angular momentum changes from}2L\to 3L\\ \text{in}5\text{seconds}\\ \text{we Rnow torgue (tau)}\\ \tau =\frac{\Delta L}{\Delta t}=\frac{L_t-L_i}{t}=\frac{3L-2L}{5}=\frac{L}{5}\\ \text{Hence, option (A) is correct.}\end{array}$