(10%) Problem 10: The upper leg muscle (quadriceps) exerts a force of FQ-1040 N,

Question

(10%) Problem 10: The upper leg muscle (quadriceps) exerts a force of FQ-1040 N, which is carried by a tendon over the kneecap (the patella) at the angles shown in the figure. 550 75° ©theexpertta.com 50% Part (a) Find the magnitude of the force, in newtons, exerted by the kneecap on the upper leg bone (the femur) at the point P Grade Summary Deductions Potential 0% 100% 78 9 sinO cotan asin0 tan(O acos Submissions Attempts remaining: 3 (4% per attempt) detailed view cosO atanOacotan)sinh) cosh) tanh)cotanhO END Degrees Radians BACKSPACE DEL CLEAR Submit Hint I give up! Hints: 4% deduction per hint. Hints remaining: 2 Feedback: 5% deduction per feedback /S 50% Part (b) What angle does the force from the kneecap act at, in degrees measured counterclockwise from the positive x-direction shown in the figure?

Explanation / Answer

Given,

Fq = 1040 N

The net force in vertical direction will be:

Fy = Fq (sin55 - sin75)

Fy = 1040 (sin55 - sin75) = -152.64 N

The net force in horizontal direction will be:

Fx = Fq (cos55 + cos75)

Fx = 1040 (cos55 + cos75) = 865.69 N

So the net force will be:

Fnet = sqrt (Fx^2 + Fy^2)

Fnet = sqrt (865.69^2 + -152.64^2) = 879.04 N

Hence, Fnet = 879.04 N

b)Theta = tan^-1(Fy/Fx)

theta = tan^-1(-152.64/865.69) = -9.99 deg

Hence, theta = -10 deg or 190 deg CCW from positive X

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