a quaterback throws the football to a staionary receiver who is 23.5 m down the filed. if the football is thrown at an initial angle of 35 to the ground at what inital speed must the quaterback the ball for it to reach the receiver 5s later?

Answer 1

You have over defined this problem.
Once you say 23.5 meters in 5 seconds you have set the horizontal speed
u = 23.5/5

Now if you set the angle at 35 then
u = initial speed * cos 35
so solve for the initial speed

However now we have a dilemna.
Vi = initial speed up = initial speed * sin 35

that means we can calculate how high it will be after 5 seconds
h = height of quarterback hand + Vi (5) - 4.9 (25)
that h better be around the height of a receiver we hope.