Chapter 8233P8.38The total mechanical energy of the skysurfer-Earth system isEKUmvmghgmech=+ =+122.Since the skysurfer has constant speed,dEdtmvdvdtmgdhdtmgvmgvmech=+=+−=−0af.The rate the system is losing mechanical energy is thendEdtmgvmech2kgm sm skW===75 09 8060 0441....bgej.*P8.39(a)Let mbe the mass of the whole board. The portion on the rough surface has mass mxL. Thenormal force supporting it is mxgLand the frictional force is µkmgxLma=. ThenagxLk=opposite to the motion.(b)In an incremental bit of forward motion dx, the kinetic energy converted into internalenergy is fdxmgxLdxkk=. The whole energy converted is12222020mvmgxLdxmgLxmgLvgLkLkLkk====zµµSection 8.5Relationship Between Conservative Forces and Potential Energy
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