Brain Teasers
Wheel 2
Consider a vertical wheel of radius 10 cm. Now suppose a smaller wheel of radius 2 cm, is made to roll around the larger wheel in the same vertical plane while the larger wheel remains fixed. What is the total number of rotations the smaller wheel makes when its center makes one complete rotation about the larger wheel?
Answer
The correct answer is 6 rotations. Suppose you rotate the smaller wheel and the larger wheel together without rolling through one rotation clockwise, the small wheel has rotated through 1 turn clockwise. Now rotate the larger wheel back to its original position counter-clockwise through one rotation at the same time holding the center of the small wheel in the original position but allowing the wheel to rotate without sliding. It will rotate through 5 more turns due to the ratio of the circumferences of the wheels. The total number of rotations of the small wheel is 5 + 1 = 6.Hide Answer Show Answer
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