Problem
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PROBLEM 214

A local sports complex has an enormous flagpole at the end of one of its fields.  In order to raise the (equally enormous) flag, they connect a line (in red) to the top of the flag, run the line to the top of the flagpole, and then down to a small electric cart (in yellow) which pulls the flag up as it is driven around the perimeter of a semicircular track at the end of the field.  See the figure on the left.  Suppose the field is 150 ft across, the cart moves at a constant speed of 20 feet per second, and the flag reaches the top exactly when the cart has reached the far side of the field.  At what speed is the flag rising when it is half-way up the flagpole?  When is the flag rising the fastest?   

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2005 Alberto L. Delgado