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* BIO Dumbbell lift IA woman lifts a 3.6-kg dumbbell in each hand with her arm in a horizontal position at the side of her body and holds it there for 3 s (see Figure P8.53) What force does the deltoid muscle in her shoulder exert on the humerus bone while holding the dumbbell? The deltoid attaches 13 cm from the shoulder joint and makes a
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- (a) What force should the woman in Figure 9.45 exert on the floor with each hand to do a push-up? Assume that she moves up at a constant speed. (b) The triceps muscle at the back of her upper arm has an effective lever arm of 1.75 cm, and she exerts force on the floor at a horizontal distance of 20.0 cm from the elbow joint. Calculate the magnitude of the force in each triceps muscle, and compare it to her weight. (c) How much work does she do if her center of mass rises 0.240 m? (d) What is her useful power output if she does 25 pushups in one minute?arrow_forwardTorque 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 P8.17arrow_forwardMany of the elements in horizontal-bar exercises can be modeled by representing the gymnast by four segments consisting of arms, torso (including the head), thighs, and lower legs, as shown in Figure P8.15a. Inertial parameters for a particular gymnast are as follows: Note that in Figure P8.l5a rcg is the distance to the center of gravity measured from the joint closest to the bar and the masses for the arms, thighs, and legs include both appendages. I is the moment of inertia of each segment about its center of gravity. Determine the distance from the bar to the center of gravity of the gymnast for the two positions shown in Figures P8.15b and P8.15c. Figure P8.15arrow_forward
- A bowling ball rolls up a ramp 0.5 m high without slipping to storage. It has an initial velocity of its center of mass of 3.0 m/s. (a) What is its velocity at the top of the ramp? (b) If the ramp is 1 m high does it make it to the top?arrow_forwardA meter stick is supported by a knife-edge at the 50-cm mark. Doug hangs masses of 0.40 and 0.60 kg from the 20-cm and 80-cm marks, respectively. Where should Doug hang a third mass of 0.30 kg to keep the stick balanced?a. 20cmb. 70cm c. 30cm d. 25cmarrow_forwardA 5.0-m-long,15-kg level plank is supported by two pivots that are resting on level ground at opposite ends of the plank. A 70-kg construction worker is standing 1.5 from the right pivot. What is the magnitude of the force of the left pivot on the plank? a. 80 N b. 130 N c. 180 N d. 230 N e. 280 Narrow_forward
- If you hold your arm outstretched with palm upward, as shown, the force to keep your arm from falling comes from your deltoid muscle. The arm of a typical person has mass 4.0 kg and the distances and angles shown in the figure.a. What force must the deltoid muscle provide to keep the arm in this position?b. By what factor does this force exceed the weight of the arm?arrow_forwardView Policies Current Attempt in Progress Concept Simulation 9.1 illustrates how the forces can vary in problems of this type. A hiker, who weighs 668 N, is strolling through the woods and crosses a small horizontal bridge. The bridge is uniform, weighs 4590 N, and rests on two concrete supports, one on each end. He stops 1/6 of the way along the bridge. What is the magnitude of the force that a concrete support exerts on the bridge (a) at the near end and (b) at the far end? (a) Number i Units (b) Number Unitsarrow_forwardQ2) Machine Curls and the Biceps Muscle. A woman performs seated machine curls to strengthen her biceps muscles (the figure below). She uses a weight of 10 kg. Horizontal distance between her elbows (A) and the bottom of the frictionless pulley (B) is 60 cm. Vertical distance between the same points is 20 cm. Determine the force exerted by the holding bar on the woman's hands when her arm is at 45° with the horizontal. At that moment, the weight has an upward acceleration of 3 m/s2. DB DIA 32cm 20cm PAB 45 60cmarrow_forward
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