Question

PROBLEM 2 Knee Extension - The angular motion of the lower leg about the knee joint, and the forces and torques produced by the muscles crossing the knee joint during knee flexions and extensions have been investigated by a number of researchers utilizing different experimental techniques. One of these techniques is discussed here. Consider the person illustrated in Fig. 10.12. The test subject is sitting on a table, with the back placed against a back rest and the lower legs free to rotate about the knee joint. The subject's torso is strapped to the back rest and the right thigh is strapped firmly to the table. A well-padded sawhorse is placed in front of the subject to prevent hyperextension at the knee joint (not shown in Fig. 10.12). An electrogoniometer is attached to the subject's right leg. The arms of the goniometer are aligned with the estimated long axes of the thigh and shank, and the axis of rotation of the goniometer is aligned with the estimated axis of rotation of the Fig. 10.12 Knee extension knee joint. The subject is then asked to extend the lower leg as rapidly as possible. The signals received from the electrogoniometer's potentiometer are stored in a computer, and are used to calculate the angular displacement of the lower leg as measured from its initial vertical position. Using a finite difference (numerical differentiation) technique, the angular velocity o and angular acceleration a of the lower leg are also computed.

Answer 1

Given; 0= 60 Wasrulls d=200 rad/se klason azucm, b=22cm B=240 Io=0.25 kg-mt

(a) from Newton's second low of motion the netoterque Mo generated abour the knee joiner is - Mo=food = 16.25) (200) = 50 Nom (cew) The near torque produced in Knee joint is Mo = 50 N-m (cup (b) Note that Mo u the magnitude of the not-Torque about the knee joint and it includes the rotational effects of all of the external forces acting on the lower leg Relative to the knee joiner there are two external files with rated and effects pateller tendenthat and weishe of the lower leg kl. fof the position of the lower leg Theurmakes an angle O=60 with the vertical, the lever alm of the Patellee cam fendon force relative to o is estimated to be azoou There she the iterque generated by Fom relcitive too is Muzafm (coo). on the otherhand he is download The torque generused by a asny ok Mwa Wabasinob (co). Therefore the magnitude of the neer. torque Mo, ascer the knee joker doare to Fa and wis Mo=Mm-Mw = afm-bulsino, fm = Mothkl sino a Fu = 50+ 0.22750/fin 660) -=146&N ciou The tension in putellal tendon is IM=14581