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Homework Help: Projectile motion - Finding velocity (not given time or angle)

  1. Nov 1, 2009 #1
    1. The problem statement, all variables and given/known data

    A baseball is hit so that it reaches a maximum height of 20.0m and travels 90.0m before hitting the ground. With what velocity is the ball hit?

    3. The attempt at a solution

    I'm confused, i went into trying to find the time but i couldn't without a given angle. I went to say that 20.0 is the peak so time to the peak would double for the total time but couldn't get time.

    This also blocked me to find the initial velocity of y and x.

    need help please.
  2. jcsd
  3. Nov 1, 2009 #2

    Fine, you were on the right track.

    I ask you two questions - what are the expressions for greatest distance and highest distance?

    You have been given two pieces of data, right? Make an equation, man!

    Distance traveled is 90 m. From this piece, you can get a relation between speed and angle.

    Also, from the peak being 20 m above, you can get another relation between speed and angle.

    That'd be enough, actually!
  4. Nov 1, 2009 #3
    yea got the equation now, solved it in the shower haha. Thanks for the reply
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