Chapter 8247P8.71Applying Newton’s second law at the bottom (b) and top (t) of thecircle givesTmgmvRbb−=2and −− =−gmvRtt2Adding these givesTT mgmvvRbt=++−222ejAlso, energy must be conserved and ∆∆UK+=0So, vmgR2020−+−=bgand vRmg4−=Substituting into the above equation gives g6.mgvtT tmgT bvbFIG. P8.71P8.72(a)Energy is conserved in the swing of the pendulum, and thestationary peg does no work. So the ball’s speed does notchange when the string hits or leaves the peg, and the ball
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