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Unformatted text preview: Determine the work done by F on an object moved counterclockwise around each box, starting at the lower left corner. ~ t I I FIGURE 8-26 Problems 1, 2. Solution
(Figure 8-26 is a plane view of the horizontal surface. over which the block js moved, showing the paths \ (<i) and (b). The force of friction is JLmgopposite to (the displacement (t . dr = - f dr), so W(a} -p,mg(f + e) = -2p,mge, and W(b} = -p,mg../i.2+li -..;2JLmgf.. Since the work done depends on the path, <friction is not a conservative force. = = It t t t t t t t t. tttt t t t t t tt t t t t t t t
(a) (b) FIGURE 8-22 Problem 3. ".Problem
. Now take Fig. 8-26 to lie in a vertical plane, and 2. find the work done by the gravitational force as an object moves from point 1 to point 2 over each of the paths shown. Solution
The path around the square consists of four segments, each along a side, in the direction of a counterclockwise circulation. Thus ..Take the origin at point 1 in Fig. 8-26 with the :zraxis horizontal to the right and the y-axis vertical upward....
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