4.38.Set Up:Let be upward. The rock has mass For a chain of negligible weight thetension is the same at all points in the chain.Solve: (a)The free-body diagram for the rock is given in Figure 4.38.Figure 4.38(b)gives The tension in thetop link, the bottom link and the middle link is 179 N.4.39.Set Up:Take to be upward. The mass of the bucket is and the mass of the chain isThe chain also has an upward acceleration of Solve: (a)Consider the chain and bucket as a combined object of mass andweight The free-body diagram is shown in Figure 4.39a. is the tension in the top link. gives and Figure 4.39(b)Apply to the bucket. The free-body diagram (Figure 4.39b) gives so (c)Apply to the bottom half of the chain. The free-body diagram is shown in Figure 4.39c. The bottomhalf of the chain has mass and weight is the tension in the middle link of the chain.gives Reflect:Part (b) can also be done by applyingto the chain. The free-body diagram is given inFigure4.39d. gives and which agrees with the value obtained previously. The tension increases from the
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