Question

Stars originate as large bodies of slowly rotating gas.Because of gravity, these clumps of gas slowly decrease in size.The angular velocity of a star increases as it shrinks because of__.
A.) law of universal gravitation
B.) conservation of linear momentum
C.) conservation of energy
D.) conservation of mass
E.) conservation of angular momentum

Answer 1

Answer:

E.) conservation of angular momentum

Explanation:

The angular momentum is defined as:

$L=r$ x $mv$

where $r$ is the radius of the star, $m$ is the mass and $v$ the angular velocity.

and angular momentum is an amount that is conserved, so the angular momentum before the star is compressed must be equal to the angular momentum after the star was compressed:

$r_{1}$ x $mv_{1}=r_{2}$ x $mv_{2}$

the second radius is smaller than the first radius, since the star shrinked, the second angular velocity must be greater that the first.

In other words, the angular velicity increases as the star shrinks because of the conservation of angular momentum.