As an interstellar cloud of hydrogen gas shrinks in size, its rate of rotation
A) increases, because its angular momentum is conserved.
B) decreases, because its angular momentum is conserved.
C) increases, because its total energy is conserved.
D) increases, because the force of gravity strengthens as the cloud shrinks.
E) decreases, because the force of gravity strengthens as the cloud shrinks.

Question

Quizplus · Accepted Answer

As the cloud shrinks in size, its moment of inertia decreases, which means that to conserve its angular momentum, it must increase its rate of rotation. This is known as the conservation of angular momentum, which states that the total angular momentum of a system remains constant unless acted upon by an external torque. Therefore, the rate of rotation of the cloud must increase.

As an Interstellar Cloud of Hydrogen Gas Shrinks in Size