Kicking a Field Goal: Initial Speed Needed for Clear Crossbar

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SUMMARY

The discussion centers on calculating the initial speed required for a football to clear a crossbar at a height of 3.05 meters, given a kick angle of 53 degrees and a horizontal distance of 10.98 meters. Participants emphasize using the equations of motion, specifically Voy = Vosin(theta) and Vox = Vocos(theta), alongside horizontal and vertical motion equations. The key insight is that the initial velocity (Vo) may not be necessary to determine the required speed, as the equations can be manipulated using the known distance and height.

PREREQUISITES
  • Understanding of projectile motion principles
  • Familiarity with trigonometric functions in physics
  • Knowledge of kinematic equations for horizontal and vertical motion
  • Basic grasp of gravitational acceleration (g = 9.81 m/s²)
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  • Study the derivation of projectile motion equations
  • Learn how to apply trigonometric identities in physics problems
  • Explore examples of solving for unknowns in kinematic equations
  • Investigate the impact of varying launch angles on projectile trajectories
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This discussion is beneficial for physics students, educators teaching introductory physics, and anyone interested in understanding the mechanics of projectile motion and its applications in sports.

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Homework Statement


If the ball is kicked at 53 degrees above horizontal what must the initial speed be if it is just to clear the crossbar. I know the ball is distance in the x direction is 10.98 m and the height of the goal post is 3.05 m.


Homework Equations


I think I should be using the equations Voy=Vosin(theta) and Vox=Vocos(theta)


The Attempt at a Solution


No idea how to solve without having any veclocities to plug into the above equations.
 
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Welcome to the PF. I moved your thread from Advanced Physics to Introductory Physics.

You have listed two of the equations that you will need to solve the problem. Now list the equation for motion x(t) in the horizontal direction, in terms of Vx(t) and Vox and t. And list the equation for motion in the vertical direction y(t), in terms of Vy(t) and Voy and t and the acceleration of gravity g.

With those equations of motion, and the ending (x,y) point you are given, do you see how you may not need to know the initial velocity Vo?
 

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