Use your fingers to:

• Change sensor positions (blue bars).
• Select Time mode (measures the time interval between the two sensors) or Speed ​​mode (measures the speed of the object as it passes the sensor).
• Turn on and off the Electromagnet that holds the steel ball.
• Click the Reset button to return the ball to the electromagnet.

The error $\alpha$ is generated by a random variable. That is, each time the fall time or speed is calculated, a value $\alpha$ is drawn within the range $[-\epsilon, \epsilon]$ and summed to the time or speed reported on the device. $\epsilon$ is the amplitude of the noise. The value of $\alpha$ is made up of two parts: random error (~Gaussian distribution around the calculated value) and systematic error (offset added to the calculated value).