(a) What is the maximum frictional force in the knee joint of a person who suppo

Question

(a) What is the maximum frictional force in the knee joint of a person who supports 59.0 kg of her mass on that knee if the coefficient of static friction is 0.016?

____N

(b) During strenuous exercise, it is possible to exert forces to the joints easily ten times greater than the weight being supported. What is the maximum force of friction under such conditions? The frictional forces in joints are relatively small in all circumstances except when the joints deteriorate, such as from injury or arthritis. Increased frictional forces can cause further damage and pain. Assume that the coefficient of kinetic friction in the joint is 0.015.

____N

Explanation / Answer

a)f <= uk N => fmax = us N= 0.016 (59.0 kg) (9.80 m/s2 ) = 9.2512 N

b) Using information from part (a),
f <= uk N=0.015(9.2512)(59.0 kg)(9.80 m/s2 )

=80.235 N

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