Question

The Saint Louis Rams nearly lost a play-off game after field-goal kicker Jeff Wilkins sent a 132 ft. field-goal attempt (that is, he kicked the ball from the 34 yard-line) straight into the goal-post cross-bar, which is 10 ft. above the ground. He kicked the 2 lb. ball at an angle of a = 30°. 10 feet 132 feet- Treat the ball as a point mass, and neglect wind resistance. (a) (20 pts) What is the velocity v, with which the ball was kicked? (b) (10 pts) If instead Wilkins kicked the ball at = 30° from the 50 yard line, the ball would have needed an initial speed of 86.1 ft/sec to slam into the cross- bar. During such a kick, the kicker's foot is in contact with the ball for 0.01 sec. What is the average magnitude of the force that would need to be applied to the ball in this case?

Answer 1

San | 10 ft %470 ho 132ft 0=30° 0 = ? Lot de direction motion : ne vo coso x t = 132 4 = 132 e to coso - bv cono 132 v 20.30 - 15 242 o ty direction motion : h = ut - 1/2gt² * 10 = 15, ainso y or ons - 07 (19. Coro)? + 10 = 132 tan 30 - 113952096 © Vo = 41148 dt/sec Answer Impulse = change in momentum Ext = mv Velocity of ball mais of ball I t=0001 , m=2 lb v=86.5 ft/see-

FX0.01 = 2x8601 => [F= 17220 lbt Answer