# Physics

posted by Anonymous

A 0.45-kg ball, attached to the end of a horizontal cord, is rotated in a circle of radius 1.3-m on a frictionless horizontal surface.
If the maximum speed of the ball is 14.7 m/s, how long does it take the ball to make on rotation if it is moving at its maximum speed?

1. Damon

circumference = 2 pi R

time in seconds
= distance / speed = 2 pi (1.3) /14.7

2. Anonymous

Ohhhhhhh...
so we use the CIRCUMFERENCE, not the RADIUS. Got it. Thank you so much!

3. Damon

Yes, unless it makes a wild plunge for the center of the circle :)

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