Motion System Design

# Fun With Fundamentals: Problem 262

The answer to this problem is only a hop, skip, and a jump away.

### Problem 262: Catapult

The Miller family cat Helix doesn’t have nine lives — she has two. By day she is a sleepy, standoffish pet that amuses herself with rubber bands and feathers. By night she is a daredevil superhero, avenging justice on nasty bugs that make scary noises until the wee hours of the morning.

Until recently, some bugs had an unfair advantage: they could fly. To level the playing field, Helix enlisted the help Dr. Joompenstein, a leading leapologist specializing in hopscotchery. After giving it some thought, Joompenstein designed a set of helical springs made from 0.09-in. diameter hard-drawn wire to be strapped to Helix’s paws. Besides providing the quick leaping action Helix needs to fight crime, the springs double as deadly bug stompers. If each spring has an outside diameter of 1.25 in. and 10 coils in total, what force is needed to compress it to its solid length and squish any bug that gets under paw? The ends of the springs are plain ground.

### Winners Circle

Fun problem 260: Extended Play August, 2002
Total entries: 156
Number correct: 58 (37%)
Winner: Wen Fu, Torrington, Conn.
Wen’s prize: TurboCAD V 8.0. With the latest version of TurboCAD, you can control layers, workplanes, views, lights, and cameras from a single palette. Features include and upgraded ACIS solid modeling engine, part tree that records entire history of 3D object creation and modification in an Explorer-like palette, assemble by facet, and applying light properties to any object.

Get your creative juices flowing and send us your original problems and solutions.

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Fun With Fundamentals: Problem 263

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Fun With Fundamentals: Problem 261