You may tape a penny or two to one tech deck and leave the other one like that. Then you use a ramp to see if mass affects the height and distance something will go
I Want To Use Tech Deck For My Science Fair Project. What Can I Do?
You can get 4 tech decks and measure the speed of each tech deck to see which is faster and why or see what there weights are and see if there is a different between all 4 tech decks if there is find out why