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Re: Ball speed testing after matches
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Originally Posted by ChrisH
Assuming the measured length is 1 meter, there is a simple calibration that can be performed to check the speed tester. Simply hold it so the ball can drop through it vertically. Hold the ball close to the first sensor and drop it through. The ball speed should read 2.2 m/s.
Don't belive me? do the math! Hint d=(at^2)/2. If anybody needs more than that post here and I'll walk you through it. I figured this out for our own tester.
ChrisH
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The ball speedometer we used at STL and Waterloo had ~34.5 inch (0.876 meter) sensor spacing. For that spacing the correct speed reading for a ball released vertically just above the top sensor, with no initial velocity, would be 0.876 / sqrt( 2*(0.876)/9.8) = 2.07 meters per second. [edited several hours later; denominator is still the elapsed time, new numerator is the drop distance (incorrectly used 1 meter in original post)]
Be sure to measure the sensor spacing, and check that the actual spacing is entered in appropriate field of the LabView screen that controls the ball speedometer.
__________________
Richard Wallace
Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
 since 2003
I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
Last edited by Richard Wallace : 29-03-2006 at 22:35.
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