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Homework Help: Projectile motion

  1. Mar 21, 2008 #1
    [SOLVED] Projectile motion

    1. The problem statement, all variables and given/known data
    How do you calculate the projectile motion of an object in the following question?

    John is a long jumper. He runs down a track, and jumps as far as he can horizonally. Her take-off velocity is 6.4 m s-1 at 20 degrees from the horizontal.

    a) show that the horizontal component of her initial velocity is 6.0m s-1

    b) Show that the vertical component of her initial velocity is 2.2 m s-1


    c) Explain why the horizontal component of her velocity is constant.



    3. The attempt at a solution

    I know that for a) you use vectors to solve it but I don't know what to do after that and for the others I have no idea what to do so any help is appreciated
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 21, 2008 #2

    tiny-tim

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    Science Advisor
    Homework Helper

    … right-angled triangle …

    Hi Paulo! :smile:

    For a) and b), draw a right-angled triangle.

    Can you now see what combination of horizontal and vertical speeds makes 6.4 m s-1 at 20 degrees from the horizontal? :smile:
     
  4. Mar 21, 2008 #3
    Initial velocity: 6.4 m/s

    a)Horizontal component= 6.4 * cosine20 degrees.
    >>6 m/s.
    b)Vertical component= 6.4 * sine 20 degrees.
    >>2.2 m/s.
    c)Since the velocity is constant due to the fact that there are no external forces acting in the horizontal direction, if you neglect air resistance, therefore, the horizontal velocity of a projectile is constant.

    Remember these are just for your reference.You must first follow the steps as mentioned by "tiny tim" and then look up the analytical method i have solved for you.
     
  5. Mar 21, 2008 #4
    Thanks guys for being so helpful
     
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