Meriam, Kraige & Bolton — Kinematics of Particles: Problem 2_165

2/165 After starting from the position marked with the “x”, a football receiver B runs the slant-in pattern shown, making a cut at P and thereafter running with a constant speed $v_B = 7\text{ yd/sec}$ in the direction shown. The quarterback releases the ball with a horizontal velocity of $100\text{ ft/sec}$ at the instant the receiver passes point P. Determine the angle $\alpha$ at which the quarterback must throw the ball, and the velocity of the ball relative to the receiver when the ball is caught. Neglect any vertical motion of the ball.