A remote control model airplane connected to a string is flown in a circle with a radius of 0.348 m about a fixed axis with an angular velocity of +1.47 rad/s. The plane’s throttle is increased, so that it acquires an angular acceleration of 2.18 rad/s2. After 0.490 s have elapsed since the plane sped up, what is the total acceleration ( ar) (in m/s2) of the airplane?