More projectile motion difficulties

AI Thread Summary
The discussion centers on solving a projectile motion problem involving a soccer ball kicked at 7.50 m/s at a 30° angle. To determine how long the ball is in the air, the vertical motion equations are utilized, specifically focusing on the time it takes for the ball to reach its maximum height and return to the original level. The acceleration due to gravity is noted as -9.80 m/s², and the participant is encouraged to use the quadratic formula to solve for time. Trigonometry is suggested to find the vertical component of the initial velocity, which is essential for applying the equations correctly. The solution involves calculating the time for the upward motion and doubling it for the total flight time.
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Homework Statement


A soccer ball is kicked with a speed of 7.50 m/s at an angle of 30.0° above the horizontal. If the ball lands at the same level from which it was kicked, how long was it in the air? (Neglect air resistance.)



Homework Equations





The Attempt at a Solution


I really don't know where to start, all of the equations are confusing me.
 
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This question is quadratic. What you need to find is how long the ball was in the air from when Vy=initial to Vy = 0. Your acceleration should be -9.80 m/s/. Finding the time, or the y-max (maximum height) will give you more insight as to how to solve the problem.

Vf = Vt + a(dt)? try it!
 
Sorry, how do I get y-max. I can't even begin to fill in this equation because I have only the acceleration
 
Okay. Vf = 0 (since it only goes so high if it's kicked), and Vi = 7.50 m/s. You can use deltaY= Vi(t)+1/2at^2, where your a = -9.80 m/s. Solve using the quadratic formula for t. Once you get t, you can multiply t by 2 since it takes the same amount of time for the ball to fall downward as it does going upward.
 
oh, wait. no. Get your Dy, by drawing a straight line through the middle of the pathway of the ball. use trigonometry to calculate the y part of the right triangle to get your Vi. then use the Vf=0, and then sub it into the equation to get t.
 
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