Leigh is doing a knee extension exercise using a 100 N dumbbell strapped to her ankle 40 cm from her knee joint. She holds her leg so that the horizontal distance from her knee joint to the dumbbell is 30 cm.
a. For this position, what torque is created by the dumbbell about her knee joint axis?
b. If the moment arm of the knee extensor muscles is 4 cm about the knee joint axis, what amount of force must these muscles produce to hold the leg in the position described? Ignore the weight of the leg.