(11%) Problem 7: while exercising in a fitnesscenter, a man lies face down on a
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Question
(11%) Problem 7: while exercising in a fitnesscenter, a man lies face down on a bench and lifts a weight with one lower leg by contacting the muscles in the back of the upper leg. 50% Part (a) Find the magnitude of the a angular acceleration produced given the mass lifted is 9.5 kg at a distance of 26 5 cm from the knee joint, the moment of inertia of the lower leg is 0,89 kgm2, the muscle force is 1250 N, and its effective perpendicular lever arm is 2.85 cm. net W sin0 cotan0 asin0 atan0 acotan0 sinho 4 5 6 Attempts remaining per attempt) cotanhO ans 0 Hint I give up! Submission History Answer Hints TA·LLC 29Explanation / Answer
(A) torque = (1250 x 0.0285) - (0.265 x 9.5 x 9.8 )
= 10.95 N m
torque = I alpha
10.95 = (0.89) alpha
alpha = 12.31 rad/s^2
(b) wf^2 - wi^2 = 2 alpha theta
w^2 - 0 = 2 x 12.31 x (19.5 x pi / 180)
w^2 = 8.38 rad^2 / s^2
Work done = change in KE
= I w^2 /2 - 0
= 0.89 x 8.38 / 2
= 3.73 J
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