Atruck with 48-in.-diameter wheels is traveling at 45 mi/h.
(
a. find the angular speed of the wheels in rad/min.
rad/min (
b. how many revolutions per minute do the wheels make?
rev/min

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  A. v = r*w where v is the outer velocity (50 mi/hr) and r is the radius (48 in) 

Doing a few conversions, we get that 50 mi/hr = 52800 in/min 

w = v/r = (52800 in/min)/(48 in) = 1100 rad/min 

B. 1 rev = 2pi rad so do a unit conversion 

(1100 rad/min)*(1 rev / 2pi rad) = 175.07 rpm