Concept explainers
Dental hygiene. Electric toothbrushes can be effective in removing dental plaque. One model consists of a head 1.1 cm in diameter that rotates back and forth through a 70.0° angle 7600 times per minute. The rim of the head contains a thin row of bristles. (See Figure 9.26.) (a) What is the average angular speed in each direction of the rotating head, in rad/s? (b) What is the average linear speed in each direction of the bristles against the teeth? (c) Using your own observations, what is the approximate speed of the bristles against your teeth when you brush by hand with an ordinary toothbrush?
Figure 9.26 Problem 26.
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