Basic Biomechanics 5th Edition by Susan Hall

Exercise 7

The patellar tendon attaches to the tibia at a 20° angle 3 cm from the axis of rotation at the knee. If the tension in the tendon is 400 N, what is the resulting acceleration of the 4.2 kg lower leg and foot given a radius of gyration of 25 cm for the lower leg/foot with respect to the axis of rotation at the knee?