Question

A constant torque acting on a uniform circular wheel changes its angular momentum from $A_0$ to $4A_0$ in $4$ seconds. The magnitude of this torque is

• A. $\frac{3A_0}{4}$
• B. $A_0$
• C. $4A_0$
• D. $12A_0$

Answer 1

The correct option is A $\frac{3A_0}{4}$

As we know,
$\tau =\frac{\Delta L}{\Delta t}$
Given,
Initial angular momentum $=A_0$
Final angular momentum $=4A_0$
Time taken to change angular momentum $A_0$ to $4A_0=4\text{s}$
Hence,
Magnitude of torque, $\tau =\frac{\Delta L}{\Delta t}$
$=\frac{4A_0-A_0}{4-0}=\frac{3A_0}{4}$