Question

A friction welding machine is butt-welding two steel pipes together. Initially the spinning pipe is rotating against the stationary pipe at a rate of 𝑓𝑟𝑝𝑚=740 rpm (rounds per minute). 25 seconds later the spinning pipe comes to rest and the molten steel between the two pipes begins to cool. Assuming that the deceleration of the moving pipe was uniform, how many revolutions did the moving pipe make before coming to rest?

I know that you have to figure out the uniform deceleration, but I don't know exactly how to do that.

Answer 1

do not worry about radians / second^2
Since you never use a length (radius) here you do not have to do 2 pi radians/second = 1 revoultion /second
Just leave your velocity in revs/sec and your acceleration in revs/second^2
average revs/s = (740/2)/60 = 740/120 revs/s
total revs = (740 / 120) 25 s