1. The problem statement, all variables and given/known data You are asked to design an airplane propleller to turn at 2400 rpm. The forward airspeed of the plane is to be 75.0 m/s, and the speed of the tips of the propeller blades through the air must not exceed 270 m/s. What is the maximum radius the propeller can have? With this radius, what is the acceleration of the propeller tip? 2. Relevant equations v = rw alpha = omega^2 (r) 3. The attempt at a solution My issue with this problem is after trying to understand the explained solution. This problem is an example in my physics book. Both the book and I convert the 2400 rpm into rad/s (2400(2)pi)/60 = 251 rad/s This is where I get confused. I simply divide as so, v= rw , so v/w = r 270/251 = 1.07 m The book doesn't do this, instead it says V_tip^2 = V_plane^2 + V_tan^2 = V_plane^2 + (r^2)(w^2) They then solve for r and get r = 1.03 vs what I got, 1.07. What exactly are they accounting for is I think what I am trying to understand. Thanks in advance.