b) What is the force of the femur on the tibia? Enter the x component, then the
ID: 1286866 • Letter: B
Question
b) What is the force of the femur on the tibia? Enter the x component, then the y component.
A person exercises the quadriceps as shown. The diagram on the right shows a model of the leg, where the person's lower leg of length L = 0.52 m is held at an angle ?1 = 55½ with respect to the horizontal. The quadriceps muscle exerts a force FM via the tendon that attaches to the tibia at a distance d = 0.145 m from the knee, in order to lift a weight of mass m1 = 7.0 kg that is attached to the foot. The tendon makes an angle of ?2 = 16½ with respect to the tibia. exercising the quadriceps a) What is the force required to hold the weight at the position shown in the diagram? Assume the person's lower leg weighs 150 N and its centre of mass is located a distance L/2 from the knee. b) What is the force of the femur on the tibia? Enter the x component, then the y component.Explanation / Answer
a) sum torques about knee
F d sin theta2 - m1 g L cos theta1 - mleg g L/2 cos theta1 = 0
F*0.145*sin(16 degrees) - 7*9.81*0.52*cos(55 degrees) - 150*0.52/2*cos(55 degrees)=0
F=1072 N
b)
sum forces in the x
x - F cos(theta1 + theta2) =0
x = 1072*cos( 71 degrees)= 349 N
now y direction
y + 1072*sin(71 degrees) - 7*9.81 - 150 = 0
y=-794 N
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