The large quadricepsmuscle in the upper leg ter-Quadriceps- Tendonminates at its lower end in a- Tibiatendon attached to the upperend of the tibia (Fig. P8.35a).The forces on the lower legwhen the leg is extended aremodeled as in Figure P8.35b,where T is the force of ten-asion in the tendon, w is theforce of gravity acting onthe lower leg, and F is theforce of gravity acting on thefoot. Find T when the ten-25.0° Tdon is at an angle of 25.0°with the tibia, assuming thatw = 30.0 N, F = 12.5 N, andthe leg is extended at anangle 0 of 40.0° with the ver-Figure P8.35tical. Assume that the centerof gravity of the lower leg is at its center and that the tendonattaches to the lower leg at a point one-fifth of the way downthe leg.13

The forces are resolved into components parallel and perpendicular to the tibia, the magnitude of…

Answered: The large quadriceps muscle in the…

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter10: Rotational Motion

Section: Chapter Questions

Problem 79P

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Torque and the Two Conditions for Equilibrium 17. The arm in Figure P8.17 weighs 41.5 N. The force of gravity acting on the arm acts through point A. Determine the magnitudes of the tension force Ft, in the deltoid muscle and the force Fs exerted by the shoulder on the humerus (upper-arm bone) to hold the arm in the position shown. Figure P8.17
A cook holds a 2.00-kg carton of milk at arm's length P8.19). What force FB must be exerted by the biceps muscle? (Ignore the weight of the forearm.) Figure P8.19
In order to get his car out of the mud, a man ties one end of a rope to the front bumper and the other end to a tee 15 m away as shown below. He then pulls on the center of the rope with a force of 400 N, which causes its center to be displaced 0.30 m, as shown. What is the force of the rope on the car?
In exercise physiologystudies, it is sometimesimportant todetermine the location ofa person’s center of gravity.This can be done withthe arrangement shownin Figure P8.21. A lightplank rests on two scalesthat read Fg1 = 380. N andFg2 = 320. N. The scales are separated by a distance of 2.00 m.How far from the woman’s feet is her center of gravity?
Find the x- and y -coordinates of the center of gravity for theboomerang in Figure P8.12a, modeling the boomerang as inFigure P8.12b, where each uniform leg of the model has alength of 0.300 m and a mass of 0.250 kg. (Note: Treat the legslike thin rods.)
A person bending forward to lift a load “with his back”(Fig. P8.23a) rather than “with his knees” can be injured bylarge forces exerted on the muscles and vertebrae. The spinepivots mainly at the fifth lumbar vertebra, with the principalsupporting force provided by the erector spinalis muscle inthe back. To see the magnitude of the forces involved, and tounderstand why back problems are common among humans,consider the model shown in Figure P8.23b of a person bendingforward to lift a 200.-N object. The spine and upper bodyare represented as a uniform horizontal rod of weight 350. N,pivoted at the base of the spine. The erector spinalis muscle,attached at a point two-thirds of the way up the spine, maintainsthe position of the back. The angle between the spineand this muscle is 12.0°. Find (a) the tension in the back muscleand (b) the compressional force in the spine.
A dental bracket exerts a horizontalforce of 80.0 N on a toothat point B in Figure P8.6. What isthe torque on the root of the toothabout point A?
A 500.-N uniform rectangular sign 4.00 mwide and 3.00 m high is suspended from ahorizontal, 6.00-m-long, uniform, 100.-N rodas indicated in Figure P8.25. The left end ofthe rod is supported by a hinge, and the rightend is supported by a thin cable making a30.0° angle with the vertical. (a) Find the tensionT in the cable. (b) Find the horizontaland vertical components of force exerted onthe left end of the rod by the hinge.
A 1 200-N uniform boom atϕ = 65° to the horizontal is supportedby a cable at an angle θ =25.0° to the horizontal as shownin Figure P8.34. The boom ispivoted at the bottom, and anobject of weight ω = 2 000 Nhangs from its top. Find (a) thetension in the support cable and (b) the components of the reaction force exerted by the pivoton the boom.
Find the x- and y-coordinates of the center of gravity of a4.00-ft by 8.00-ft uniform sheet of plywood with the upperright quadrant removed as shown in Figure P8.11. Hint:The mass of any segment of the plywood sheet is proportionalto the area of that segment.
A uniform 35.0-kg beam of length, 5 5.00 m is supported by a verticalrope located d 5 1.20 m fromits left end as in Figure P8.18. Theright end of the beam is supportedby a vertical column. Find (a) thetension in the rope and (b) theforce that the column exerts onthe right end of the beam.
The chewing muscle, the masseter, is one of the strongest in the human body. It isattached to the mandible (lower jawbone) as shown in Figure P8.33a. The jawbone ispivoted about a socket just in front of the auditory canal. The forces acting on the jawboneare equivalent to those acting on the curved bar in Figure P8.33b.

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