During a knee extension exercise there are two forces that are producing torque at the knee joint. One is the quadriceps muscle and the other is the weight at the ankle joint. The quad is capable of producing 500 Newtons of force, while the weight at the ankle is 10 kg. The distance from the knee joint to the quad force is 0.05 meters and the distance from the knee joint to the weight is 0.38 meters (these are not the moment arms). The knee is flexed to 125 degrees. Draw and calculate the moment arms for each force on the picture below and decide if the joint flexes or extends.

 

biomechanics please.