Question

Points:2 What is the angular momentum of a figure skater spinning (with arms in close to her body) at 3.38 evolutions per second, assuming her to be a uniform cylinder with a height of 1.31 m, a radius of 13.8 cm, and a mass of 56.5 kg. 11.4 kg*m 2/s Your receipt no. is 158-7050 Previous Tries How much torque is required to slow her to a stop in 4.54 s, assuming she does not move her arms? You are correct. 2516 N"m Submit Answer Incorect. Tries 5/S0 Previous Tries

Answer 1

given
angular speed, w1 = 3.38 rev/s = 3.38*2*pi rad/s
hence
w = 21.23 rad/s

height, h = 1.31 m
radius r = 13.8 cm = 0.138 m
mass, m = 56.5 kg

moment of inertia, I = 0.5mr^2 = 1.075986/2 kg m^2
hence
angualr momentum L = Iw = 11.42159139 kg m^2 rad/s

now, torque required to stop in t = 4.54 s, T = L/t
hence
T = 2.51576 Nm