CHAPTER 12 HOMEWORK
1. (p.323 Ex.10) A uniform steel beam has a mass of 1100kg. On it is resting half of an identical beam, as shown in Fig. 12-55. What is the vertical support force at each end?
2. (p.325 Ex.26) Calculate the tension FT in the wire that supports the 30.0kg beam shown in Fig. 12-68, and the force FW exerted by the wall on the beam (give magnitude and direction).
3. (p.326 Ex.47) How much pressure is needed to compress the volume of an iron block by 0.10 percent? Express answer in N/m2, and compare it to atmospheric pressure (1.0 x 105N/m2).
4. (p.327 Ex.49) Shear forces as shown in Fig. 12-24 are applied to a steel plate that is 0.50m on a side and 1.1cm thick. The shear strain produced by these forces is 0.050. Calculate the magnitude of the force.
5. (p.327 Ex.55) (a) What is the minimum cross-sectional area required of a vertical steel cable from which is suspended a 320-kg chandelier? Assume a safety factor of 7.0. (b) If the cable is 7.5m long, how much does it elongate?
*6. (p.326 Ex.38) A person wants to push a lamp (mass 7.2kg) across the floor, where the coefficient of friction is 0.20 (Fig. 12-76). Calculate the maximum height above the floor at which the erson can push the lamp so that it slides rather than tips.
*7. (p.327 Ex.59) Parachutists whose chutes have failed to open have been known to survive if they landed in deep snow. Assume that a 75-kg parachutist hits the ground with an area of impact of 0.30m2 at a velocity of 60m/s, and that the ultimate strength of body tissue is 5 x 105N/m2. Assume that the person is brought to rest in 1.0, of snow. Show that the person can escape injury.