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Homework Help: Projectile motion - velocity and distance

  1. Sep 16, 2012 #1
    Projectile motion -- velocity and distance

    1. The problem statement, all variables and given/known data
    A projectile is launched with an initial speed of 60 m/s at an angle of 30 degrees above the horizontal. The projectile lands on a hillside 4 seconds later. Neglect air friction. What is the projectile's velocity at the highest point of it's trajectory? What is the straight line distance from where the projectile launched to where it hits it's target?

    2. Relevant equations

    3. The attempt at a solution
    For my B I got 207 m but the answer in the book says 212 m.
    Last edited: Sep 16, 2012
  2. jcsd
  3. Sep 16, 2012 #2


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    Staff: Mentor

    Re: Projectile

    Can you please show us your work step-by-step? That will make it easier to help you.

    Also, I will add a bit to your one-word thread title -- please try to make your thread titles very descriptive of the specific question you are asking in the thread.
  4. Sep 16, 2012 #3
    Re: Projectile motion -- velocity and distance

    I'm not exactly sure how to use symbols, but my work is as follows. First I split the vector into the x and y components. I got the vector component x to be 51.961523423 and the vector y component to be 30. The I used the formula: final velocity squared equals initial velocity squared plus 2 times change in y time acceleration. The initial velocity is 30 m/s. The change in y is 2 times velocity times 1/2 time plus acceleration times 1/2 times time squared. I get the cahnge in y to be 40.4 I got the final velocity to equal 10.4. That is incorrect. For part b I used x=vt velocity is 51.96152423 and the time is 4 seconds. multiplied I get 207.
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