A truck with 0.420-m-radius tires travels at 32.0 m/s. What is the angular velocity of the rotating tires in radians per second? What is this in rev/min?
OpenStax College Physics, Chapter 6, Problem 7 (Problems & Exercises)
Why is it not 76.2/2pi*60 (why is pi multiplied by the 60 not the 2
Hi goblinking88, thank you for the question. Do you mean in the calculator screenshot? This is just the way I tend to enter things into the calculator. The 76.2 is getting divided by both the 2 and by the pi, so I type it in as 76.2/2/pi. Then it gets multiplied by 60. All together it looks like 76.2/2/pi*60. The "pi" is not multiplied by 60, but rather the result of 76.2/2/pi is multiplied by 60.
Hope this helps,
Hi shaun, I think you entered it in the calculator wrong. The answer should be 7.18 x 10^3 rev/min. We would not multiply pi by 60.
Hi benjamin, thank you for your comment. The answer shown in correct. I think there is confusion about the concise way I'm typing into the calculator. Ans/2/pi*60 is the same as the more verbose . Since the calculator evaluates from left to right, it's the result of Ans/2/pi which is multiplied by 60. Multiplying by 60 seconds per minute is necessary since, without doing so, the units would be "revolutions per second", whereas the goal is to have units of "revolutions per minute" - rpm, in other words.
All the best,