4rpm = 16 in/min, so
1 rev = 4in
2πr = 4, so r = 2/π
for the 8" wheel, the ratio of radii is 8/(2/π) = 4π
So, if its radius is 4π as big, its speed is 1/(4π) as fast, or 16/(4π) = 4/π in/min
It makes 1/(4π) * 4 = 1/π rpm
Your unknown radius is ok, but I don't see how you got the speed. The 8" wheel's radius is about 12 times as big, so it will be turning about 1/12 as fast.
A point on the rim of a wheel of unknown radius in a pulley system has a velocity of 16 in/min. The wheel is making 4 rpm. If the radius of the other wheel is 8 inches, find the 8" wheel's rpms and the unknown wheel's radius.
I got a radius of about 0.637" for the unknown wheel and an rpm of about 2.548 for the 8" wheel. Did I get it correct?
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