# How fast is the rock traveling?

A rock is twirled in a horizontal circle overhead on a string with a frequency of 30 revolutions per minute. If the radius of the circle is 35cm. How fast is the rock traveling?

### 2 Answers

Relevance

- oubaasLv 72 months agoFavorite Answer
period T = 1*60/30 = 2.00 sec

angular speed ω = 2PI/T = PI rad/sec

tangential speed V = ω *r = 3.1416*0.35 = 1.10 m/sec

- SlowfingerLv 62 months ago
The rock covers 30 circle perimeters per minute.

One perimeter is 2rπ so the total path is

s = 30 * 2rπ = 60 * 35 * π = 6597 cm

Because time for this path is 1min, the speed is also

v = 6597 cm/min = 65.97 m/min = 1.1 m/s (rounded)

General formula is

v = 2 r π f

where

r is radius

f is frequency

Still have questions? Get your answers by asking now.