Motion System Design

# Fun with Fundamentals: Problem 266

Problem 266//For goodness snake
Don’t let this one choke you up.

One sunny Summer afternoon, Katie Scratch was eating macaroni and cheese on her front porch with her pet snake Vladmir. Suddenly and without warning, the young girl began choking on her pasta. Because their mom had run to the store to pick up lettuce and tomatoes, it was up to Vladmir to save his beloved Katie.

Dragging her by the shoelaces to her tricycle, he managed to get her on the vehicle and get it going down the street towards the hospital by pedaling with his tail. But just as Katie and Vladmir reached the hospital driveway, the tricycle began to speed up and careen out of control towards the hospital’s windmill generators. Slamming into one of them, the tricycle was totaled and the windmill was badly damaged — blades knocked off and axle leaning on another windmill. Luckily, the crash dislodged the macaroni and cheese from Katie’s throat, saving the girl’s life. Unluckily, the windmills are the main source of power to the hospital. If each windmill produces electricity as long as its axle is spinning, how long will the damaged one give juice after it is knocked over? Assume the axle’s mass is 40 kg, its radius is 150 cm, and its coefficient of kinetic friction is 0.2.

Solution to problem 265 Pressure’s on, February 2003