*13-112. The pilot of an airplane executes a vertical loop which in part follows the path of a "four-leaved rose,"r = (-600cos 20) ft, where 0 is in radians. If

his speed is a constant vp = 80 ft/s, determine the vertical reaction the seat of the plane exerts on the pilot when the plane is at A.He weights 130 lb. Hint: To determine the time derivatives necessary to compute the acceleration components a,and a, take the first and second time derivatives of r = 400(1 + cos®). Then, for further information, use Eq. 12–26 to determine é. Also, take the time derivative of Eq. 12-26, noting that vp = 0 to determine Ô.