11.44.Model:Model Sam strapped with skis as a particle, and apply the law of conservation of energy. Visualize:Solve:(a)The conservation of energy equation is 1g1th0g0extKUEKUW++Δ=++The snow is frictionless, so th0 J.EΔ=However, the wind is an external force doing work on Sam as he moves down the hill. Thus, extwind1g10g0222211001010wind()()110 J(0 J)2222WWKUKUmvmgymvmgymvmgymvmgyWvgym==+−+⎛⎞⎛⎞=+−+−+=−⎜⎟⎜⎟⎝⎠⎝⎠⇒=+We compute the work done by the wind as follows: windwindwindcos160(200 N)(146 m)cos16027,400 JWFrFr=⋅Δ=Δ°=°=−GGwhere we have used /sin 20146 m.rh°=Now we can compute 212( 27,400 J)2(9.8 m/s )(50 m)15.7 m/s75 kgv−=(b)We will use a tilted coordinate system, with the
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