The skater turns his skate so that friction slows his angular speed to 18 rad/s

Question

The skater turns his skate so that friction slows his angular speed to 18 rad/s over a period of 21.0 s. Find the average net torque acting on the skater during this time interval. What To Do? Consider the figure skater and how you should set about finding the average net torque acting on him. (a) Which Approach? (b) For What Reason? (c) Which Expresses the Concept? Angular Impulse-Momentum Theorem Angular Momentum Conservation Correct: Your answer is correct. No external torques act on the object External torques change angular momentum Correct: Your answer is correct. script L = 0 script L = net(avg)t Correct: Your answer is correct. (d) Use the variables I, i, and f, avg, and t as needed to symbolically express the concept in part (c). Incorrect: Your answer is incorrect. = Incorrect: Your answer is incorrect. (e) What was the average net torque on the skater? avg =

Explanation / Answer

torque = I * alpha

alpha = wf-wi/ t = -18/21 = -6/7 rad/s^2

change in angular momentum with time = torque

dL/dt = t

tavg = I*6/7

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