College Physics

Figure 9.15If the pencil is displaced even slightly, a torque is created by its weight that is in the same direction as the disp ...

Figure 9.17(a) The center of gravity of an adult is above the hip joints (one of the main pivots in the body) and lies between t ...

Check the solution to see if it is reasonableby examining the magnitude, direction, and units of the answer. The importance of ...

different.) Logically, the right hand should support more weight, since it is closer to the cg. In fact, if the right hand is mo ...

PhET Explorations: Balancing Act Play with objects on a teeter totter to learn about balance. Test what you've learned by trying ...

(9.32) MA = Fo Fi = li lo . This equation is true for levers in general. For the nail puller, the MA is certainly greater than o ...

Discussion An even longer handle would reduce the force needed to lift the load. The MA here isMA = 1.02 / 0.0750 = 13.6. Anothe ...

Figure 9.26(a) The combination of pulleys is used to multiply force. The force is an integral multiple of tension if the pulleys ...

Figure 9.27(a) The figure shows the forearm of a person holding a book. The biceps exert a forceFBto support the weight of the f ...

which yields FB= 470 N. (9.38) Now, the combined weight of the arm and its load is⎛⎝6.50 kg⎞⎠⎛⎝9.80 m/s^2 ⎞⎠= 63.7 N, so that th ...

Figure 9.28(a) Good posture places the upper body’s cg over the pivots in the hips, eliminating the need for muscle action to ba ...

FB (9.42) wub+wbox= 4200 N 833 N = 5.04. This force is considerably larger than it would be if the load were not present. Soluti ...

center of gravity: dynamic equilibrium: mechanical advantage: neutral equilibrium: perpendicular lever arm: SI units of torque: ...

whereτis torque,ris the distance from the pivot point to the point where the force is applied,Fis the magnitude of the force, an ...

11.Why are the forces exerted on the outside world by the limbs of our bodies usually much smaller than the forces exerted by mu ...

Problems & Exercises 9.2 The Second Condition for Equilibrium 1.(a) When opening a door, you push on it perpendicularly with ...

assuming no friction between the legs and the sidewalk. (b) What force is exerted by each side on the hinge? Figure 9.35A sandwi ...

Figure 9.38The knee joint works like a hinge to bend and straighten the lower leg. It permits a person to sit, stand, and pivot. ...

Figure 9.42The muscles in the back of the leg pull the Achilles tendon when one stands on one’s toes. A simplified lever system ...

318 CHAPTER 9 | STATICS AND TORQUE This content is available for free at http://cnx.org/content/col11406/1.7 ...