1. The problem statement, all variables and given/known data "A car is traveling at 100 km/h and the tire of the car has a radius of 36cm. Find the number of revolutions per second." 3. The attempt at a solution 100 km/h * (10,000,000 cm/km) * (1h/3600 secs) = 2777.77777778 cm/s is the speed of the car. Θ = a/r Θ = (2777.78) / (36) Θ = 77.16 To find number of revolutions, we must divide by 2pi. 77.16/2pi = 12.28 revolutions/sec. That is the correct answer. a) I did not get that on the quiz because I do not understand the mechanics behind the operation. Can anyone walk me through each calculation and state why that step is done? b) And why is 2777.78 cm/s equal to the arc length? Isn't arc length a distance? I thought 2778.78 cm/s was a velocity measurement. Thank you.