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

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Homework Help Overview

The problem involves a quarterback throwing a football a distance of 60 yards at a 45-degree angle, and the original poster seeks to determine the speed of the throw. The context is rooted in kinematics and projectile motion.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply equations of motion in both x and y directions to solve for the throw speed. There is uncertainty about the appropriate value for displacement in the y-direction equation, leading to questions about whether it should be zero.

Discussion Status

Participants are exploring the implications of the throw's measurement and its relation to the height of the throw and catch. Some guidance has been offered regarding the use of net displacement in the equations of motion, and the discussion appears to be progressing towards a clearer understanding.

Contextual Notes

There is a consideration of the net displacement in the y-direction being zero, as the ball is caught at the same height from which it was thrown. This assumption is under discussion and affects the approach to solving the problem.

xcgirl
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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?
 
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When the throw has been measured as having gone 60 yards, what does that mean? Is the ball still flying through the air?
 
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.
 
xcgirl said:
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...
 
thanks, i got it now!
 

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