1. The problem statement, all variables and given/known data Can free fall acceleration be determined by dropping a marble through a single photogate? The CPO timer attached to the photogate can measure the time it takes for the marble to pass between the arms. Knowing the diameter of the marble enables one to calculate the speed. If the marble is dropped just above the IR beam, the initial velocity can be assumed to be zero. Therefore, the dropping distance is the diameter of the marble. However, my calculations are showing a ridiculously large value for g. What am I doing wrong? 2. Relevant equations Δy = ½aΔt2 3. The attempt at a solution 1) I looked up information on how to determine g using photogate. All information points to using two photogates or a picket fence. 2) The diameter of the marble is 1.9 cm and the time taken by the marble to cross the IR beam is 0.0457 seconds. Since the marble is dropped just above the beam, vi =0. Using the equation; Δy = ½aΔt2, a = 2*Δy/Δt2 = 2*0.019/0.04572 = 18.19 m/s2 The logic and reason makes complete sense to me, but the numbers are not what I am expecting. What am I doing wrong? Thanks in advance.