You perform a knee extension exercise on a cable type machine
during which your knee joint rotates through an angular displacement of 0.84
radians in 2.24 s. This lift is done entirely by the quadriceps muscle which
shortens 0.021 m. At the beginning and end of that time the weight is
motionless. That action, together with the various ratios in the machine
causes a weight of 43.06 N to be lifted a total of 0.351 m. What was
was the force produced by your quadriceps muscles during the lift?