Concept explainers
8.121 and 8.123 A cable is placed around three parallel pipes. Two of the pipes are fixed and do not rotate; the third pipe is slowly rotated. Knowing that the coefficients of friction are μS = 0.25 and μk = 0.20, determine the largest weight W that can be raised (a) if only pipe A is rotated counterclockwise, (b) if only pipe C is rotated clockwise.
Fig. P8.120 and P8.121
(a)
Find the largest weight W that can be raised only when the pipe A is rotated counter clockwise.
Answer to Problem 8.121P
The largest weight W that can be raised only when the pipe A is rotated counter clockwise is
Explanation of Solution
Given information:
The coefficient of static friction is
The coefficient of kinetic friction is
Calculation:
Show the free-body diagram of the pipes A, B, and C as in Figure 1.
Find the angle of the cable wounded around the pipe as follows;
Find the largest weight W using the equation.
Substitute 0.25 for
Therefore, the largest weight W that can be raised only when the pipe A is rotated counter clockwise is
(b)
Find the largest weight W that can be raised only when the pipe C is rotated clockwise.
Answer to Problem 8.121P
The largest weight W that can be raised only when the pipe C is rotated clockwise is
Explanation of Solution
Given information:
The coefficient of static friction is
The coefficient of kinetic friction is
Calculation:
Show the free-body diagram of the pipes A, B, and C as in Figure 2.
Find the angle of the cable wounded around the pipe as follows;
Find the largest weight W using the equation.
Substitute 0.25 for
Therefore, the largest weight W that can be raised only when the pipe C is rotated clockwise is
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Chapter 8 Solutions
Vector Mechanics for Engineers: Statics
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