Raspberry Pi Zero Helmet Impact Force Monitor
jenfoxbot 
But Wait! What is Impact Force??
Fortunately, the term "impact force" is pretty straightforward: the amount of force in an impact. Like most things though, measuring it requires a more precise definition. The equation for impact force is:
where F is the impact force, KE is the kinetic energy (energy of motion), and d is the impact distance, or how much the object crunches.
There are two key takeaways from this equation:
- Impact force is directly proportional to the kinetic energy, meaning that the impact force increases if the kinetic energy increases.
- Impact force is inversely proportional to impact distance, meaning that the impact force decreases if the impact distance increases. (This is why we have airbags: to increase the distance of our impact.)
Force is typically measured in Newtons (N), but impact force may be discussed in terms of a "G-Force", a number expressed as a multiple of g, or earth's gravitational acceleration (9.8 m/s^2). When we use units of G-force, we are measuring an objects acceleration relative to free fall towards the earth. Technically speaking, g is an acceleration, not a force. However, it is useful when talking about collisions because acceleration (the change in speed and/or direction) is what damages the human body.
For this project, we'll use G-force units to determine if an impact is potentially dangerous and deserving of medical attention. Research has found that g-forces above 9G can be fatal to most humans (without special training), and 4-6G can be dangerous if sustained for more than a few seconds.
Knowing this, we can program our impact force monitor to alert us if our accelerometer measures a G-force above either of these thresholds. Hooray, science!
For more information, read about impact force and G-force on Wikipedia!