Quote: a train wheel has a diameter of 30 inches to the rim, which rests on the track. the flange,which keeps the wheel from slipping off the track, projects 1 inch beyond the rim. when the train is traveling 60 mph, what is the linear velocity in mph of a point on the outer edge of the flange?
fun question
Ok there are basically two parts to solving this.
First, given that the train moves forward at 60 mph we have to figure out how fast the wheel is spinning. This is called it's angular frequency and is measured in revolutions/second.
Then given it's angular frequency and the distance to a point on the flange d the linear velocity is
point on flange linear speed = 2*pi*d*(angular frequency)
We have to assume there is no slippage between the wheel and the track.
The wheel makes one circumference for every complete revolution.
In this case this is 2*pi*30 inches = 60 pi inches/revolution
60 mph = 60*5280*12/3600 inches/second = 1056 inches/second
So the wheel has angular velocity of
1056 inches/second / (60 pi inches/revolution) = 88/(5 pi) revolutions/second
Now the flange is 31 inches from the center. So it will have linear velocity of
88/(5 pi) (revolution/second) * 2*pi*31 inches/revolution = 88*2*31/5 = 5456/5
and to put this back into mph we have
5456/5 inches/second * 3600/(12*5280) sec/hr /(inches/mile) = 5456*3600/(5*12*5280) = 62 mph.