An ice skater has a moment of inertia of 5.0 kg. M^2 when her arms are outstretched , and at the time she is spinning at 3.0 rev/s . If she pulls in her arms and decreases her moment of inertia to 2.0 kg. M^2 , how fast will she be spinning

The ice skater will spin at an angular speed of 7.5 revolutions per second.

Explanation:

From statement we notice that ice skater can be considered as a system, on which no external forces are exerted, such that Principle of Angular Momentum can be applied:

(Eq. 1)

Where:

- Moment of inertia of the ice skater when her arms are outstretched, measured in kilogram-square meters.

- Angular speed when arms are outstretched, measured in revolutions per second.

- Moment of inertial of the ice skater when her arms are pulled, measured in kilogram-square meters.

- Angular speed when arms are pulled, measured in revolutions per second.

If , and , the angular speed when arms are pulled is:

The ice skater will spin at an angular speed of 7.5 revolutions per second.

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray