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

Adding distance to a spherical projectile by use of backspin

  1. Jan 9, 2007 #1
    In the following setup, there is a pressureised chamber that has a valve which opens up and leads to a barrel housing a spherical projectile. When valve is opened, the ball will go through the barrel.

    I am trying to determine the best location for "port holes" that will give the ball backspin.

    Im thinking that as the ball moves forward, a high pressure area will be a higher pressure at top and lower pressure at bottom. When the air moves, it will cause friction that will give the ball backspin... I think...

    Attached Files:

  2. jcsd
  3. Jan 11, 2007 #2
    Should I post this in another forum section?
  4. Jan 11, 2007 #3


    User Avatar
    Science Advisor
    Gold Member

    Don't know about your holes, but what if you roughen the top of the pipe (it's slick everywhere else) so the ball rolls a little?
  5. Jan 11, 2007 #4
    The entire wall must be slick.
  6. Jan 11, 2007 #5


    User Avatar
    Science Advisor
    Gold Member

    Adding too many holes in the barrel will significantly reduce the pressure driving the projectile, and therefore reduce its exit velocity.

    Perhaps slightly curving the barrel so that the ball rolls along the top of the barrel before exiting? Nothing too significant, just a few degrees...
  7. Jan 11, 2007 #6
    another constraint is that the barrel can not be curved :(.

    The holes would decrease the pressure, but i believe that although exit velocity would be less, perhaps the backspin generated would compensate.
  8. Aug 5, 2011 #7
    try to fix the lower end of the valve instead of creating holes...
    as only the upper half of the valve opens, the pressure will force the top half of the ball with higher pressure( as the valve outlet is reduced). Top spin will automatically be generated as the force is on the upper half of the ball.
    If you cannot fix the lower half of the valve, atleast try to block the lower section adjacent to the lower half of the valve, this will give the came result.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook