0.750 m -1.50 m 2.25 m C Figure P12.12

$ 4 101 R F V A uniform, aluminum beam 9.00 m long, weighting 300 N, rests symmetrically on two supports 5.00 m apart. A boy weighing 600 N starts at point A and walks toward the right. (Figure 1) Figure < 1 of 1 % f5 5 T G B f6 Y H OD & N 7 B f8 * 4+ 00 8 M fg K ly 9 Part A How far beyond point B can the boy walk before the beam tips? VE ΑΣΦ ? 1 = Submit f10 | Request Answer Part B How far from the right end of the beam should support B be placed so that the boy can walk just to the end of the beam without causing it to tip? IVE ΑΣΦ ? 8:44 P 5/29/202 BA P 8 O 1 = Submit 99+ L alt Request Answer Pearson f11 hulu f12 ctrl [ + (6 = الالالال ins prt sc m ] pause m delete backspace ^ V home Review | Constants enter num lock T shift end 7 home ↑ A end

When you bend over, a series of large muscles, the erector spinae, pull on your spine to hold you up. Figure shows a simplified model of the spine as a rod of length L that pivots at its lower end. In this model, the center of gravity of the 320 N weight of the upper torso is at the center of the spine. The 160 N weight of the head and arms acts at the top of the spine. The erector spinae muscles are modeled as a single muscle that acts at an 12° angle to the spine. Suppose the person shown bends over to an angle of 30° from the horizontal. a. What is the tension in the erector muscle? Hint: Align your x-axis with the axis of the spine.b. A force from the pelvic girdle acts on the base of the spine. What is the component of this force in the direction of the spine? (This large force is the cause of many back injuries).

Two people carry a heavy electric motor by placing it on a light board 2.10 mm long. One person lifts at one end with a force of 450 NN, and the other lifts the opposite end with a force of 570 NN. What is the weight of the motor? Express your answer in newtons.   Where along the board is its center of gravity located? Express your answer in meters.     Suppose the board is not light but weighs 190 NN, with its center of gravity at its center, and the two people each exert the same forces as before. What is the weight of the motor in this case? Express your answer in newtons.   Where is its center of gravity located? Express your answer in meters.