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Homework Help: Ball is hit up in to the air

  1. Aug 25, 2008 #1
    Ball is hit up in to the air....

    Question:
    A baseball is hit almost straight up into the air with a speed of about 41 m/s.
    (a) How high does it go? (m)

    (b) How long is it in the air? (s)

    I think you probably just have to multiply or divide this number (41 m/s) by some sort of wind resistance ratio or number, but I have no idea what this would be since I've never had physics before and my teacher insists we don't need a book for this class.

    Please help give me the tools and I can figure it out.
     
  2. jcsd
  3. Aug 25, 2008 #2

    Defennder

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    Re: Ball is hit up in to the air....

    a)You have the standard 3 kinematics equations, right? Use them. Note that the only acceleration here is the one due to gravity, which is constant.

    b)Same approach as before.

    EDIT:You want to consider "wind"? That becomes difficult, especially if the wind is blowing upwards or downwards. You didn't provide any details as well.
     
  4. Aug 25, 2008 #3
    Re: Ball is hit up in to the air....

    Like I said, I have no book and I am a week into (one class so far) my first physics class ever. So, NO I don't have kinematics equations or any idea what that is.
     
  5. Aug 25, 2008 #4

    Defennder

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    Re: Ball is hit up in to the air....

    How would you do this without any equations? You may not need a textbook but you would surely need notes. If you're not given the equations, then you can look them up online on Google.
     
  6. Aug 25, 2008 #5
    Re: Ball is hit up in to the air....

    I guess that's why I'm here. Because I couldn't do it.

    I looked up the equations already. They call for acceleration, time, displacement, and velocity inputs on different variables.

    I guess I am looking for displacement, but I am only given velocity. What do I do about the other two variables?
     
  7. Aug 25, 2008 #6

    LowlyPion

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    Re: Ball is hit up in to the air....

    This post addresses the equations you will need:

    https://www.physicsforums.com/showpost.php?p=905663&postcount=2

    Your initial velocity vo = 41 m/s
    You should ignore any wind considerations and the gravity constant you need is 9.8 m/s2
     
  8. Aug 25, 2008 #7
    Re: Ball is hit up in to the air....

    Ok thanks, I think I need this equation:

    x = x0 + v0(t) + (1/2) a t^2

    In order to find how high, I am looking for x, right? That stands for displacement I assume.

    So, I would substitute to get x= 0 + 41(t) + (1/2)(9.8)(t^2). Original position (xO) should be zero, right? Since it starts at the ground... and what should time be?
     
  9. Aug 25, 2008 #8
    Re: Ball is hit up in to the air....

    ....?
     
  10. Aug 26, 2008 #9

    LowlyPion

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    Re: Ball is hit up in to the air....

    You might figure the time a little differently first. You know that Vo is 41 m/s and you know that gravity will act to slow that down at 9.8 m/s2. The time to do that then is found with v=at or in this case you can solve for t with t = Vo/g were g is the 9.8 m/s2

    Knowing the time then let's you find the distance with the simpler form of the equation x = 1/2 g * t2
     
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