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PROBLEM 10.47
A block of weight
W
is pulled up a plane forming an angle
α
with the
horizontal by a force
P
directed along the plane. If
µ
is the coefficient of
friction between the block and the plane, derive an expression for the
mechanical efficiency of the system. Show that the mechanical efficiency
cannot exceed
1
2
if the block is to remain in place when the force
P
is
removed.
SOLUTION
Input work
P x
δ
=
( )
Output work
sin
Wx
αδ
=
Efficiency:
sin
sin
or
W
Px
P
δα
ηη
==
(1)
0:
sin
0
or
sin
x
FP
F
W
P
WF
αα
Σ=
−−
=
=
+
(2)
0:
cos
0
or
cos
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This note was uploaded on 07/11/2011 for the course EGM 2511 taught by Professor Jenkins during the Spring '08 term at University of Florida.
 Spring '08
 Jenkins
 Statics

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