Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Football Filled with Helium

  1. Sep 25, 2005 #1
    Hey guys,

    in an article it states:

    Why is this true? What other info can I obtain from this/what info is missing/what is (in)accurate?

    From what I can think of myself. The reason of why this would happen is that since helium is lighter, the force the helium particles are exerting on the football are much less of that of air therefore you will need to pump more helium into the football to recieve that same amount of pressure that is required.

    Am I correct on this statement?

    Also would the helium even be able to help keep the football in the air for a longer period of time as apposed to a football filled with air? I mean the skin of the football is still pretty heavy, so would the helium be able to lift the football and counter the force of gravity on the ball even for a short period of time?

    Any input would be appreciated. Thanks!
  2. jcsd
  3. Sep 25, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    HINT: Compare the weight of air molecules in a given volume with a given temperature with the weight of helium molecules in the same volume with the same temperature.
  4. Sep 26, 2005 #3
    but this is to be more of a physics related question, so i don't think this would help that much although i will look into it

    no one can even help start a discussion on this!?

    another though... re-arranging F = ma we get a = F/m therefore if the football is thrown with the same force, but the mass of the ball is lighter, the ball will have greater acceleration which would cause a farther distance or hang time? is this correct?
    Last edited: Sep 26, 2005
  5. Sep 27, 2005 #4

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    The lighter helium ball experiences more buoyancy than the heavier air filled ball. This is just Archimedes principle. Since hang time depends on the net downward acceleration, the reduced downward force on the lighter ball (due to the upward buoyant force) reduces the downward acceleration and increases the hang time.

  6. Sep 27, 2005 #5


    User Avatar

    Also, the flight medium is easier to travel through, so the football would move even more quickly.
  7. Sep 27, 2005 #6


    User Avatar
    Science Advisor

    I don't follow that. The flight medium is still air, the football still has the same size and shape. Why would filling a football with helium make the "flight medium" easier to travel through?

    A crucial point here is "PV= NRT". Assuming same pressure, volume, temperature a football filled with helium would contain exactly the same number of helium atoms as one filled with air would contain air molecules. Heliums atomic weight is 4, nitrogen's (air is mostly nitrogen) is 14 so air would be approximately 14/4 or 3 1/2 times as heavy as helium (hmm, I don't remember whether He molecules are He2 or if Nitrogen is...).

    Of course, it is quite possible that even the weight of air in a football is only a fraction of an ounce. Most of the weight of a football is in the cover.
  8. Sep 27, 2005 #7
    B r I N Cl H O F
    Those are the diatomic gases
  9. Sep 27, 2005 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    IIRC, the effects of air resistance are like the inverse of the mass, so a less massive football would suffer more losses due to drag, thus not travel as far. But as Halls said most of the mass of a football is in the skin so all of these effects will be 2nd order, which means they may be barely measurable. Perhaps less of an effect then a wet or dry football.
  10. Sep 27, 2005 #9
    great discussion thanks! i dont think there can be much more said about this unless theres thorough experimenting about this topic.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook