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Unformatted text preview: 6-24.The work iscosWFs=where is the angle between the force and displacement vectors.(3.0)(12)cos036WNmJ==6-29.The work of force is equal to the change in kinetic energy2211cos22fiFsmvmv=-The force of friction is opposite in direction to the displacement, so = 180o.221122cosfimvmvFs-=22()2 cosfim vvFs-=27626293(1.67 10)((2.0 10/ )(5.0 10/ ) )1.8 102(0.010 10)cos180kgm sm sFNm----==6-30.Work done = change in PEG()fiWmg hh=-2(200)(9.81/)(1.5)29432.9Wkgm smkJ===6-31.Change in PEG = Work done + Work of friction force()cosfifrmg hhWF s-=+()cosfifrWmg hhF s=--The force of friction is opposite in direction to the displacement, so = 180o.2(200)(9.81/)(1.5)(150)(7.0)cos18039934.0Wkgm smNmkJ=-==6-33. (a) The lifting force acting on the woman is equal to the weight of the woman because womansspeed is constant. Both lifting force and displacement are directed upward. The work done on the woman iscoscos0WFsmghmgh===2(60.0)(9.81/)(3.0)1765.8 1.8Wkgm smkJ===(b) The woman walks up at constant speed, so the lifting force must equal the weight of the...
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