I am building a machine for my martial arts club so that I can have a bit of fun and measure the speed and reaction times of my club mates.(adsbygoogle = window.adsbygoogle || []).push({});

The design that I feel would yield the most reliable and accurate results would be to mount an upside down 'pendulum' on a frame. At the head of the pendulum would be a padded punching surface, the other end would be steel rod axis mounted on bearings connected to a optical rotary encoder. (rotation/angle measuring sensor)

The theory being that you hit the pad and a computer measures the nanoseconds between a given angle. Do a bit of high-school geometry and you can find the m/s acceleration and multiply it by the weight of the 'pendulum' to find the g-force. (F = MA) But...

Q1) What is the mass of punched bag?

I hope its as simple as this: if I removed the 'pendulum' from the machine and it weights 1kg. Then lay it down, with a fulcrum at the axis and scales under the head end, the head end weights 750grams. Would I be correct in guessing that the head end weight (750grams) would be use to calculate g-force? Or do I some how need to include the whole 1kg mass of the whole 'pendulum'?

2) Do you think I would need to bother dialing-out the effects of gravity? Or would the be somewhat insignificant give that the measures will be taken in the first 45 degrees (start from vertical position)

I hope that makes sence! Many thanks in advance :)

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# Measuring punching G-Force on a Pendulum

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