One of the most basic things students do in a physics lab is to collect data and use that to build a model. Most of these models come in the form of a mathematical function. But here is the problem.

The iPhone makes it easy to do all kinds of cool physics. Like, say, use the change in velocity in an elevator to measure the height of a building.

A horizontal line means the object is moving at a constant speed. The gradient of the line = the rate of change of speed. The steeper the line, the greater the increase in speed. The area under the ...