Galileo’s inclined plane
Exhibit on display in Stanislaw Lem Garden of Experiences, a branch of the Museum of Municipal Engineering in Krakow.
Description written by Michał Urban
What we see here is an inclined plane. It’s a metal track, 6 meters long, supported on posts. The track slopes down gently, in a straight line. The inclination is 15 degrees. Mounted within the walls of the track are metal elements that serve as bells – they make a sound when the ball rolls over them. Notice that the bells are placed in increasingly greater distances from one another, as you move down the track. The ratio of the distances is the same as that of consecutive odd numbers: 1, 3, 5, 7, 9 and so on.
You’ll find the ball in the lower part of the track. Move it to the upper end and think: what will be the frequency of the pings made by the bells, as the ball strikes them rolling down the track?
Now, release the ball and listen for the frequency of the pings. Turns out it is constant – the bells ring in equal time intervals, despite the increasing distance between them. This is because the ball rolls faster and faster, accelerated by the component force of gravity that is parallel to the track, thus compensating for the increasing distances between the bells. The first experimenter, who studied motion of bodies on an inclined plane was Galileo Galilei.