Question

Please help with exercise portion of this problem. Can you also show how you arrived at your answer. Thank you!

PRACTICE IT

A merry-go-round modeled as a disk of mass M = 7.50 x 10¹ kg and radius R = 2.10 m is rotating in a horizontal plane about a frictionless vertical axle.

(a) After a student with mass m = 84.0 Kg jumps onto the merry-go-round, the system's angular speed decreases to 1.95 rad/s. If the student walks slowly from the edge toward the center, find the angular speed of the system when she reaches a point 0.530 m from the center.

Correct answer: 5.52 rad/s

(b) Find the change in the system's rotational kinetic energy caused by her movement to the center.

Correct answer 1872 J

(c) Find the work done on the student as she walks to r = 0.530 m.

Correct answer -343 J

Exercise

Use the values from the PRACTICE IT section to answer this exercise.

(a) Find the angular speed of the merry-go-round before the student jumped on, assuming the student didn't transfer any momentum or energy as she jumped on the merry-go-round.

??????

(b) By how much did the kinetic energy of the system change when the student jumped on? Notice that energy is lost in this process, as should be expected, since it is essentially a perfectly inelastic collision.

KE_f - KE_i = ???????? J

Answer 1