A loaded penguin sled weighing 80N rests on a plane inclined at 20\' to the hori
ID: 2092497 • Letter: A
Question
A loaded penguin sled weighing 80N rests on a plane inclined at 20' to the horizontal. Between the sled and the plane, the coefficient of static friction is 0.25 and the coefficent of kinetic friction is 0.15
A) Draw and lable a free body diagram for the sled.
B)what is the minimum magnitude of the force F (parallel to the slope) that will prevent the sled from slipping down the slope?
C)What is the minimum value of F that will start the sled moving up the slope?
D)what value of F is needed to move the sled up the slope at constant velocity ?
Explanation / Answer
a)I am not drawing a free bod diagram.
the gravity acts downward. it can be broken into 2 parts, one parallel to the plane and the other perpendicular.
the parallel part is 80Sin20 and the perpendicular part is 80Cos20.
The friction is above the plane.
b)Maximum static friction=us*N=0.25*80Cos20=18.8N
Gravitational force along plane=80Sin20=27.4N
F=27.4-18.8=8.60N
c)For moving up the plane, the friction acts up the plane.
F=27.4+18.8=46.2N
d)After it has started moving friction force=uk*N=11.30N
F=80Sin20+11.3=38.6N
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