There are very small sporadic changes in the speed of rotation of the earth.
Shifting of large air masses in the earth's atmosphere produce a change in the moment of inertia of the earth causing its speed of rotation to charge.

Options

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

Answer

A

Explanation

(a) Earth and moon being considered one system effect of moon on tides takes place, hence sporadic changes of speed of rotation of earth are observed.
Also from law of conservation of angular momentum we have when external torque is acting upon a body rotating about an axis, then the angular momentum of the body remains constant.
`J = I omega = constant`.
When large air masses in the earth's atmosphere shift they cause a change in moment of inertia and since angular momentum is to be maintained constant, the angular velocity or speed of rotation changes.