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Finagle J. Wurme is getting ready to live one of his lifelong dreams — auditioning for a spot on David Letterman’s Stupid Pet Tricks.

Finagle’s been training his Siamese cat, Thrasher, to ride a skateboard and things are going well. He’s now ready to take Thrasher to the next level.

Finagle is busy constructing a short track with a loop built into the middle, for Thrasher to skateboard down on the big day. But he’s not sure how high he needs to build the starting ramp for Thrasher to make it safely around the loop on his board.

Together, Thrasher and his skateboard weigh 15 lb and the radius of the loop is 5 ft. Assume there’s no friction on the track and kitty has perfect balance.

How high must Thrasher start from to be able to make it safely around the loop without falling off due to gravity?

 

I think I've solved this ... show me the solution.

 

This puzzler was originally Fun with Fundamentals Problem 298.