Question

HP 48% ) Thu Nov 21 Insert Format Tools Table Window Help SU Chapter 5 Practice Questions -Saved to my Mac gn Layout References Mailings Review View A AavĄ E A A dre XX ALATI Albcode AaBbcABCD AaB Heading 2 2. 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. s - Focus triglish (United States 01 Jom 7. TO00 «@AO WO MacBook

Answer 1

Here we apply concept of rotational equilibrium and definition of torque.

r Au quad force, Fw=500N . weight of ankle, wg= r Am Quad force, Fq = 500H weight at anale, Wa = (1079) (9.81183) = 98 N - 1- Q iaco - a=0.38m q=0.05m. 550 wo c From from diagram, we can 98 re can see, moment arm for weight IVO n

az = a Com 55° = (0.38m) Coos 55° = 0.218m moment arom for quad force, a = q (as 55° = 005) Coos 55°m = 0.0287m Now Enet = Fa qI - Waa counter clockwise clockwire Thet - (SOON) (0.008700) - (98N) (0 218m) - 14.35 Nom - 21.364 Nm. As net torque is negative je weight will pull down the leg so joint will flex not extend