A compact disc has a radius of 6 centimeters.
a. What is its circumference in meters?
b. If the cd rotates 4 times per second, what is the linear speed of a point on the outer edge of the cd? Give
your answer in meters per second.
c. What is the linear speed of a point 3 centimeters from the center of the cd? (Assume the angular speed
has not changed).

Answer :

Circumference is [tex]2\pi{r}=37.7[/tex] (approx.)
Speed is 4 times that. That is, 150.8 cm/s or 1.508 m/s.
If we get a point at distance 3 cm, we take the radius half of that. The circumference also gets half, so does the linear speed. We get 0.754 m/s or 75.398 cm/s.



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