Science Buddies: "Ask an Expert"

Hello I have a question, can I use 1 in diameter foam pipe insulation or it is strictly necessary to use 1-1/2 in diameter foam pipe insulation?

Rodrigo036,

Thank you for you question. You do not have to explicitly use a 1.5 in tube. However, the suggested diameter is to help ensure the marble is able to role free from any drag it might experience from the sides of the marble rubbing against the sides of the tube track, causing an error in the measurement of time and therefore velocity and acceleration.

Consider this: the average target marble is about 16 mm in diameter and if 1 in = 25.4 mm, then there is only 4.7 mm clearance on either side of the marble as it roles down the track instead of 11.05 mm on either side if you have a 1.5 in tube. This just gets worse if you use a marble that is larger.