My Notes O Ask Your Teache 14 O o3 points 1 Prevous Anpwers Waherd 11 P074 A stu

Question

My Notes O Ask Your Teache 14 O o3 points 1 Prevous Anpwers Waherd 11 P074 A student on a piano stool rotates freely with an angular speed of 3.27 rev/s. The student holds a 1.48-kg mass in each outstretched arm, 0.759 m from the axis of rotation. The combined moment of inertia of the student and the stool, ignoring the two masses, is 4.78 kg·m, a value that remains constant. increases to 3.54 rev/s. How far are the masses from the axis of rotation at this time, considering the (a) As the student pulls his arms inward, his angular speed masses to be points? 0.855 Your response differs from the correct answer by more than 10%. Double check your calculations. m (b) Calculate the initial and final kinetic energy of the system. (initial) (final)

Explanation / Answer

A) Since angular momentum is constant,

i1W1 = i2W2

(4.78+2*1.48*r^2) *3.54 = (4.78+2*1.48*0.759^2) *3.27

r = 0.6395 m answer

B) initial KE = 0.5i1w1^2

= 0.5*(4.78+2*1.48*0.759^2) *3.27^2

= 34.673 J

Final KE = 0.5i2w2^2

= 0.5*(4.78+2*1.48*0.6395^2) *3.54^2

= 37. 535 J

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