Description
Virtual free-fall laboratory: a steel ball held by an electromagnet falls along a vertical ruler between two adjustable-position sensors. They measure either the fall time between them (Time mode) or the instantaneous speed as the ball passes (Speed mode), with configurable artificial measurement errors (random and systematic).
Controls
Drag the sensors (blue bars) to change their positions on the ruler. On the meter, click the circles to select Time or Speed mode, turn the electromagnet holding the ball on or off, or click Restart to return the ball to the electromagnet.
Measurement errors
The error $\alpha$ is generated by a random variable: each time the fall time or speed is calculated, a value $\alpha$ is drawn from the interval $[-\epsilon, \epsilon]$ and added to the value reported by the device. $\epsilon$ is the noise amplitude. The value of $\alpha$ has two components: random error (a Gaussian distribution centered on the calculated value) and systematic error (an offset added to the calculated value).
Physical model
This reproduces the method of a real laboratory experiment: the direct measurement (time or speed) is used to estimate gravitational acceleration, including realistic measurement errors and introducing the concepts of experimental uncertainty and error propagation.
Developers
Marco P. M. de Souza