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Homework Help: Velocity under constant acceleration

  1. Jun 20, 2012 #1
    The best leaper in the animal kingdom is the puma, which can jump to a height of 3.7 m when leaving the ground at an angle of 45°. With what speed must the animal leave the ground to reach that height?

    knowns: y=3.7 yo=0 Vo=0 V=want!

    I tried finding the velocity by using the equation V^2=0+2(-9.8)(-3.7) but ended up with the wrong answer. What am I doing wrong?
  2. jcsd
  3. Jun 20, 2012 #2
    Do I need to get velocitys for the x and y components of the jump?? how do I do that?
  4. Jun 20, 2012 #3
    This is projectile motion, so you have the break the velocity into components.
  5. Jun 20, 2012 #4
    but im not given a velocity so how do I break it into components?
  6. Jun 20, 2012 #5
    The initial velocity is what you are looking. It's not zero.
    the equation you want to use is ymax=((Vo^2)sin^2(theta))/2g
    i believe
  7. Jun 20, 2012 #6
    the solution i got is 10m/s if anyone else can verify
  8. Jun 20, 2012 #7
    Hmm, I'm obviously having finger trouble because I get nearer 12 m/s.
  9. Jun 20, 2012 #8
    How do you know what the Vo is though?
  10. Jun 20, 2012 #9
    yes the answer was 12m/s
  11. Jun 20, 2012 #10
    The equation in the first post gives only the vertical component of velocity, you want the initial velocity.
  12. Jun 20, 2012 #11
    sorry about that i plugged it into my calculator on radian mode. Should have just done it in my head. It is 12m/s sorry about that i guys
  13. Jun 20, 2012 #12
    no finger trouble is on me
  14. Jun 20, 2012 #13
    What you calculated in your original message was the vertical component of the puma's velocity.

    The problem states that the puma's jumped at 45 deg from the horizontal and, as AmritpalS stated, you then need to work out what this works out as given the vertical component ... look at AmritpalS's equation and re-arrange it.
  15. Jun 20, 2012 #14
    Ok thanks yea I was just trying to solve for the wrong variable. That equation is a little new to me Ill have to remember that one.
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