A quarterback can throw 60yd @ 45 degree angle. How fast can he throw?

[xcgirl]

Homework Statement

A quarterback can throw 60yd @ 45 degree angle. How fast can he throw?

Homework Equations

60 yds = 54.86 meters

The Attempt at a Solution

x-direction
d = vt
4.86 = vcos(45)(t)

y-direction
d = vt + 1/2at^2
d = vsin(45)t + 1/2(9.8)t^2

I want to solve for t in both equations, set them equal, and use that to solve for v but I don't know what to use for d in the y-direction equation. would it be zero because it ends up on the ground?

 

[gneill]

When the throw has been measured as having gone 60 yards, what does that mean? Is the ball still flying through the air?

 

[xcgirl]

I think that it means that the ball is caught at the same height that it is thrown from, so its a net displacement in the y-direction is 0.

 

[gneill]

I think that it means that the ball is caught at the same height that it is thrown from, so its a net displacement in the y-direction is 0.

Okay, so if you put that net y-displacement into your equation of motion for the y-direction, you should be able to solve for t in terms of the other variables in that equation.

Oh, and make sure that you account for the fact that the acceleration due to gravity is in the downward direction...

 

[xcgirl]

thanks, i got it now!