posted by Elisa on .
A quarterback throws a football toward a receiver with an initial speed of 21 m/s at an angle of 30° above the horizontal. At that instant, the receiver is 12 m from the quarterback. In what direction and with what constant speed should the receiver run in order to catch the football at the level at which it was thrown?
Using d = (V^2/g)sin2µ
the distance the football travels derives from d = (21^2/9.8)sin(60) = 38.97 m.
The time it will take the ball to reach the receivers hands derives from Vf = Vo - gt or 0 = 21sin60 - 9.8t making t = 1.85 sec.
Consequently, the receiver should run away from the quarterback at a speed of (38.97 - 12)/1.85 = 14.58m/s.
that is the speed I originally got, but it is supposedly wrong.