MS-PS2 · Analysing and Interpreting Data · Newton's First Law

Your phone
felt it too

When the bus pulls away you lurch backward. Your phone, sitting in your pocket, records that same lurch as a number. Go get that number, then explain what your body already knew.

01

Record a trip

You need real data from a real ride. This takes about five minutes and one phone.

  1. Install Phyphox (free, iOS and Android).
  2. Open it and choose Acceleration (without g).
  3. Put the phone flat, screen up, somewhere it will not slide — a bag on the floor or a cup holder. Note which way the top of the phone points.
  4. Press play at the start of the ride. Stop after several starts and stops.
  5. Export as CSV and email it to yourself.
Write down what happened. Before you look at the file, note the order of events: pulled away, cruised, braked hard at a light, turned left. You will need that list to make sense of the squiggle.
02

Predict the trace

Before you open your file, draw what you expect. Above the zero line means acceleration forward, below means backward. Draw all the way across.

Your prediction
03

Load your data

Locked — predict first

Drop in the CSV Phyphox gave you. Nothing leaves this page — the file is read in your browser.

The sample is made up so you can see how the page works. It is not a real recording, and it is not evidence. Your own file is.

04

Mark the events

Locked — load data first

Click on the graph wherever something happened, then name it. Match each spike to something you actually felt.

05

Explain it

Locked
Pick one spike

Choose one clear spike. What was the vehicle doing, and which way did your body lean?

Why you leaned

Nobody pushed you. So why did you move? Use the word inertia, and say what force was actually acting on you and where it was applied.

The flat parts

Find a stretch where the trace sits near zero but the vehicle was moving fast. Why is there no acceleration when you are clearly in motion?