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Homework Help: Football punt kinetc energy

  1. Apr 28, 2009 #1
    1. The problem statement, all variables and given/known data
    A football is punted downfield (neglect the resistance of the air.)
    a.) Where in the path of the punted ball is the kinetic energy the greatest?
    b.) where in the path of the punted ball is teh potential energy teh greatest?
    c. Where in the path of the punted ball is the mechanical energy the greatest?
    d.) When the return man catches the ball what happens to the kinetc energy that the ball had?

    2. Relevant equations
    none that i know of

    3. The attempt at a solution
    a.) is it at the top when its thrown
    b. is it when its about to be kicked?
    c. i dont know this one
    d. is this there is no kinetic energy?
  2. jcsd
  3. Apr 28, 2009 #2


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    What is the potential energy formula for an object at any height?
  4. Apr 28, 2009 #3
    i dont know.. I dont think i ever learned that...
  5. Apr 28, 2009 #4


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    OK. Well time to learn that then

    PE = m*g*h

    So at what h in the flight of the ball is PE at its max?
  6. Apr 28, 2009 #5
    at the highest point?
  7. Apr 28, 2009 #6

    Now to get #1 think about how PE and KE are related. When KE is at a min, where is the PE? When KE is at a max, where is the PE?
  8. Apr 28, 2009 #7
    when KE is at a minuimum, there isnt much motion...So teh potential energy would be greater...
    So when Ke is at a max, PE would be lower
  9. Apr 28, 2009 #8
    youre certainly on the right track here.

    So you found that PE is greatest when the ball is at its maximum height. So when do you think its KE would be highest keeping in mind what you just concluded?
  10. Apr 28, 2009 #9
    also at its highest point
  11. Apr 28, 2009 #10
    How could that be so? You determined this already:

    "So when Ke is at a max, PE would be lower"

    So how can the KE in this situation be at a max when PE is at a max?

    If I were you, before you go any further look up some information on projectile motion.

    http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/Vectors/ProjectilesMotion.html [Broken]

    Here is a very basic set of equations and a diagram. Dont limit your search to this, do some of your own research on projectile motion
    Last edited by a moderator: May 4, 2017
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