Steel balls work reasonably well, also. Timers should be set out in hall and connected to power strips so that the first power strip can turn on all timers simultaneously. Timers must be capable of being spread out over the 12 meters. Extension cords will be required. Each station needs 400g of masses.
Slotted masses work fine.
Use three 100's and two 50's at each station. Unless motion probes are attached to Port 2 students should go to 'collect' and then turn on 'Force only data'. Inform students to leave carts set up this way. One roll of tape is sufficient. Masking tape will probably leave less residue on the carts.