# Find the speed of the football when it is released.

• Oct 2nd 2013, 04:23 PM
shmiks
Find the speed of the football when it is released.
What am I doing wrong...

The quarterback of a football team releases a pass at a height of 8 feet above the playing field, and the football is caught by a receiver 38 yards directly downfield at a height of 4 feet. The pass is released at an angle of https://fsulearn.ferris.edu/courses/...es/mc021-1.jpgwith the horizontal. Find the speed of the football when it is released. Round your answer to three decimal places.

Formula used:
(Vo Cosθ)t i + [ h+(Vosinθ)t - ˝gt˛] j

OK so. My method to solve this was to solve the X portion for t with respect to Vo and then plug t into the y portion to solve for Vo. 38 yards = 114 ft

Vo cosθ t = x
Vo cos(45) t = 114
t=114/Vo cos45
t= 114√2Vo

[ h+(Vosinθ)t - ˝gt˛] = y
4= 8+(Vo sin45)t -16t2
-4 =
(Vo sin45)( 114√2Vo) -16( 114√2Vo)2
-4 = 114Vo2 -16( 25992)Vo2
-4 = 114Vo2 -415872Vo2-4 = (114-415872)Vo2
-4 = -415758Vo2
-4/-415758 = Vo2
Vo= √(2/207879)Vo = .003102

 a. 19.462 feet per second b. 33.169 feet per second c. 118.732 feet per second d. 59.366 feet per second e. 190.165 feet per second

What am I doing wrong!!
This is killing me and i have quiz on it tomorrow
• Oct 2nd 2013, 07:33 PM
topsquark
Re: Find the speed of the football when it is released.
Quote:

Originally Posted by shmiks

The quarterback of a football team releases a pass at a height of 8 feet above the playing field, and the football is caught by a receiver 38 yards directly downfield at a height of 4 feet. The pass is released at an angle of https://fsulearn.ferris.edu/courses/...es/mc021-1.jpg with the horizontal. Find the speed of the football when it is released. Round your answer to three decimal places.

Check the units... Otherwise the solution method is sound.

-Dan