When you bend your knee, the quadriceps muscle is stretched.
This increases the tension in the quadriceps tendon attached to
your kneecap (patella), which, in turn, increases the tension in
the patella tendon that attaches your kneecap to your lower leg
bone (tibia). Simultaneously, the end of your upper leg bone
(femur) pushes outward on the patella. The figure shows how these
parts of a knee joint are arranged.(Figure 1)
What size force does the femur exerts on the kneecap if the
tendons are oriented as in the figure and the tension in each
tendon is 60 N?
Express your answer using two significant
?F(horiz) = 0
Fh = 60 cos 42 = 44.58
?F(vert) = 0,
Fv = 60 - 60 sin 42 = 60 - 40.148 = 19.85
F = v Fh² Fv² = v 44.58² 19.85² = 48.8