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

Projectile Measurements: RPM, Position, Velocity, acceleration

  1. Sep 10, 2011 #1
    Hello everybody,

    I'm working on a project and I want to verify a few theories I have. I'm unfamiliar with equipment for taking these types of measurements, so I wanted a little bit of help on this. Basically a bb is fired from an airsoft gun (350-550 fps), and I want to find the velocity/time, position/time, and initial muzzle rpm out of the barrel. Here is the setup I have in mind, but there has to be a better way.

    Using a high speed camera, you have distance and elevation markers. To compensate for the angle which would cause error in the height measurement, the camera would be placed at the focus of a curved "marker", and the marker will serve as a distance marker as well. The camera will be moved after a set of shots at a certain distance, the average will be taken, and the velocity will be calculated by taking the time between markers. Then plot, fit, and there is the velocity/time and position/time graphs.

    For RPM, it seems that you'd need to mark out the "equator" on the bb, and count the number of rotations per second using the high speed camera.

    Anyways, how are these measurements normally done? Sonic rangefinders for position, then take the derivative for velocity? Radar for velocity/position? Infrared laser for rpm?

    Thanks for the help guys!
  2. jcsd
  3. Sep 16, 2011 #2
    What will get you on the right track....look up (EXTERNAL BALISTICS)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook