Question

Assertion: The speed of whirlwind in a tornado is alarmingly high.
Reason: If no external torque acts on a body, its angular velocity remains conserved.

• A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion
• B. If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion
• C. If Assertion is true but Reason is false
• D. If both Assertion and Reason are false

Answer 1

Answer: (C)

In a whirlwind in a tornado, the air from nearby regions gets concentrated in a small space thereby decreasing the value of its moment of inertia considerably. Since, $I\omega =$ constant, so due to decrease in moment of inertia of the air, its angular speed increases to a high value.
If no external torque acts, then
$\tau =0$ or $\frac{dL}{dt}=0$ or $L=$ constant
or $I\omega =$ constant
As in the rotational motion, the moment of inertia of the body can change due to the change in position of the axis of rotation, the angular speed may not remain conserved.