What Are the Optimal Kicking Angles for a Field Goal in Football?

AI Thread Summary
The discussion focuses on determining the optimal kicking angles for a football field goal, specifically from a distance of 50 meters with a goalpost height of 3.44 meters. The kicker's initial speed is 25 m/s, and the equations of motion are applied to find the angles. The user initially struggles with calculations due to a calculator error but eventually resolves the problem after resetting the device. The correct angles for scoring are identified as 31 degrees and 63 degrees. The thread highlights the importance of accurate calculations in physics problems related to sports.
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Homework Statement


a football kicker can give the ball an initial speed of 25m/s. what are the least and greatest elevation angles at which he can kick the ball to score a field goal from a point 50m in font of the goalposts whose horizontal bar is 3.44 m above the ground.


Homework Equations


d = Vit + 0.5at^2

The Attempt at a Solution


Dx=distance in x direction
Dy=distance in y direction
and so on for Velocity and Acceleration

V = 25m/s
Dy = 3.44m
Vx = 25cos(theta)m/s
Vy = 25sin(theta)m/2
Ay = -9.8m/s^2

t = (Dx)/(Vx) = 50m/(25cos(theta))s

Now plug everything into an equation for Dy
Dy = Vy*t + 0.5Ay*t^2
3.44 = (25sin(theta))(2/cos(theta)) + 0.5(-9.8)(2/cos(theta))^2

I cannot get an answer for theta out of this equation..

The proper answers are 31 degrees and 63 degrees but i dot know how to solve it
 
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nevermind i think i solved it. my calculator had a setting messed up somewhere that i couldn't find and kept giving me errors.

i reset my calculator and was able to solve it.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
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