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 workkinetic energy theorem is
2
2
1
0
net
wind
1
1
2
2
K
mv
mv
W
W
Δ
=
−
=
=
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
wind
F
G
and
r
Δ
G
is
135 ,
θ
=
°
so
wind
wind
wind
cos135
(4 N)(100 m)cos135
282.8 J
W
F
r
F
y
=
⋅Δ
=
Δ
° =
° = −
G
G
Thus, her final speed is
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 Fall '09
 geller
 Energy, Force, Friction, Kinetic Energy, Work, Wwind, energy theorem, workkinetic energy theorem

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