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Homework Help: Question that I need help answering [projectile motion]

  1. Aug 23, 2006 #1
    Okay, can someone help me figure out this problem. I've tried alot of things but then i just get lost in all my sine and cosine mess that ends up confusing me.

    [values changed for simplicity reasons]

    -The pitcher is going to throw a ball from 4 meters above the ground and there is a distance of 20 m to the batter. A pitcher stands on the mound and throws the ball at an angle of @[theta] with respect to the horizon with the initial speed of 40 m/s. At what angle should the ball be thrown so that the ball will land 2 meters above the ground when it reaches the batter?

    so the data is as follows:

    initial starting point of ball: 4 meters above ground (y) and 20 meters from the batter (x)
    final point of the ball: 2 meters above the ground (y)and 20 meters from the original point (x)
    initial speed is 40 m/s at the unknown angle of @[theta]

    so basically, i guess what i'm asking here is how to split the initial velocity into x and y components.

    thank you if you can help me,
    and thanks for trying if u can't. O.O
  2. jcsd
  3. Aug 23, 2006 #2


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    You are correct that you need to take components of the initial velocity then use kinetmatic equations to solve two simultaneous equations to find [itex]\theta[/itex]. Have you taken components before? Seen any worked examples in class? It does involve a small amount of trig.
  4. Aug 23, 2006 #3
    I have, but not alot of experience outside of mechanical solving using kinematic solving that actually requires generalizations. Any help is appreciated.
  5. Aug 24, 2006 #4


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    Okay, so you know the intial speed is 40 m.s-1. This speed is has a direction of [itex]\theta[/itex] degrees above the horizontal. Now, can you use trigonometry to determine the horizontal and vertical components of the initial velocity?
    Last edited: Aug 24, 2006
  6. Aug 24, 2006 #5
    Okay thanks Hootenanny but I figured it out. Greatly appreciate it though.
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