Assertion : The speed of a whirl wind in a tornado is alarmigly high.
Reason : If no external torque acts on a body, its angualr velocity remains constant.

Options

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 reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

C

Explanation

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, `Iomega` = 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=0implies(dL)/(dt)=0` or `L=` constant `impliesIomega`=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.