Air track will be leveled. Photogates are connected to a computer. The computer program ( Precision Timer by Vernier Software) has various timing modes available. Use one photogate to find velocity of cart. OR Use two photogates to show that cart has the same velocity anywhere on track. Other timing modes where the velocity of the cart at each photogate and the travel time between the photgates can be measured and the acceleration is determined. (Acceleration can be calculated by the computer program.) Dynamic carts can be used in place of the air track.