# 1.7.2 Accelerometer

Course subject(s) Module 1: Mechanics

In this Engineering & Applications module, we want you to try out a small experiment at home. Watch the following video.

#### The App

The app we use for the first and second experiment is one you can find on the app- and playstore, named “Physics Toolbox Accelerometer“.

To set up the app like in the video:

• Open up the app.
• In the top left corner, expand the menu. Then choose “Linear Accelerometer“. This gives you the relative acceleration your phone is experiencing.
• Press the gear in the top right corner to open the settings. In the settings, under “Displayed Axis”, tick the “Show total”, and tick off the other axis buttons. This makes reading the x-y-z values easier,

#### Experiment 1: Running acceleration

This is a tricky one. You start to run from standing still, and you try to measure your acceleration. While starting to run, try to keep your phone as still as possible relative to your body.

Are you faster than Usain Bolt? The world’s fastest man achieves his record speed with a starting acceleration of nearly 1g (or  9.8 m/s²)!

#### Experiment 2: Value of local gravity

• Drop your phone on a soft place (preferably on a bed, or a giant pillow).
• You can measure your local gravity while letting it drop.
• Do this a few times, and write down the acceleration at each attempt.
• Afterwards, take the average of them to find the value of g at your place on earth!

You might notice a large spike, followed by an even larger spike. Don’t be confused, the largest spike is actually the place where your phone fell on the bed! Why is this acceleration much higher? To compare your result with your actual local gravity, you can use the “g-Force Meter” mode in the app. If your measurement deviates from your local gravity, can you tell us why? And why does your local gravity even deviate from the standard value? Leave your answers in the discussion down below!

#### Experiment 3: Cannonball

You are able to measure the velocity of an object throwing an object at a certain angle. By measuring the distance it travelled and your own height, you can calculate the velocity that the object left your hand with.

How fast are you able to throw your object? The world record shot put is set (in 1990) at a velocity of approximately 15 m/s²!