When a car with wheels of radius 14 in is driven at 35 mi/h, the wheels turn at approx. 420 rpm. How do you get this?

Question

pfenn1 · Answer

Do you know how to calculate the circumference of a circle, given the radius?

anonymous · Answer

C = 2PiR

pfenn1 · Answer

|dw:1338950124837:dw|When the wheel turns around through 1 rotation, you  will have travled one circumference of the wheel, correct?

anonymous · Answer

Yes

pfenn1 · Answer

So all you have to do is calculate the circumference of the wheel, determine how many times the wheel must turn in one hour to travel 35 miles in one hour, and then translate those many revolutions per hour into rpm (revolutions per minute).

anonymous · Answer

C = 2pi(14) = 87.96
12*5280*35 = 2217600 in
Divide the two and you get ~420!
Thank you very much!

pfenn1 · Answer

You are welcome.