All about Gravity

Gravity, about as interesting as it might get in the school yard is hearing about the proverbial apple falling on Newtons head, or if your lucky dropping some marbles of of D block…

One of the great things about inertial sensors is that they measure gravity. Gravity being 1g (0.98m/s/s for the technical), and is one of those few constants in life (along with death and taxes I suppose). This makes it a really neat component present in any signal you measure on an inertial sensor, be it your mobile phone, watch, or one of our STEMfit wearables.

Knowing there is a constant gravity signal in your wearable turns out to be really useful for example in sports like swimming, where the roll of your body, which is in time with strokes, makes a handy stroke counter. You can also measure the changes in body orientation during skydiving tricks (if you like jumping out of planes).

One area where it is particularly fascinating is where a sensor is freefalling in the air, in such a case the gravity component disappears from the signal (ask your students why? if you need to fill in 15mins of a lesson). So now that you have a measure of when an object is in free fall you can measure how long it is in free-fall. From there and thanks to the great works of Mr Newtons laws of motion you can calculate vertical height! Including everything from standing vertical jumps, BMX jumps and even a snowboarders height in a half pipe. Now that makes for a really interesting physics lesson!

Here are some of our papers if you want to know more

Wearable Sensors in sport: A practical guide https://www.springer.com/gp/book/9789811337765

Performance assessment innovations for elite snowboarding

https://www.sciencedirect.com/science/article/pii/S1877705810003425

An integrated swimming monitoring system for the biomechanical analysis of swimming strokes

Inertial monitoring of style and accuracy at 10,000 feet