11.53.Model:Use the particle model for the ice skater, the model of kinetic/static friction, and the work-kinetic energy theorem. Visualize:Solve:(a)The work-kinetic energy theorem is 2210netwind1122KmvmvWWΔ=−==There is no kinetic friction along her direction of motion. Static friction acts to prevent her skates from slipping sideways on the ice, but this force is perpendicular to the motion and does not contribute to a change in thermal energy. The angle between windFGand rΔGis 135 ,θ=°so windwindwindcos135(4 N)(100 m)cos135282.8 JWFrFy=⋅Δ=Δ° =° = −GGThus, her final speed is
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