1. The problem statement, all variables and given/known data http://apcentral.collegeboard.com/apc/public/repository/ap05_phys_laboneerror_47485.pdf The above link is an updated version of the lab that I'm currently typing up. I have already gathered all data necessary: Time taken to travel 50 meters: @ 1.089 degree downward slope: 2.513 seconds @ 2.178 degree downward slope: 1.600 seconds @ 3.269 degree downward slope: 1.169 seconds Time taken to travel 100 meters: @ 1.089 degree downward slope: 2.870 seconds @ 2.178 degree downward slope: 2.173 seconds @ 3.269 degree downward slope: 1.633 seconds 2. Relevant equations I am given the following equations: (1-1)x=x0 + vt + at^2 (1-2)v=v0 + at (1-3)a=g sin(theta) (1-4)X=1/2(g sin theta)t^2 (1-5)v= (g sin theta) (1-6)S=1/2 (g sin theta)t^2 [This is in a graph of S vs. t^2) 3. The attempt at a solution My question is: How do I use all these equations to work out a value of G? It states in my lab handout that "... a plot of t^2 versus S should yield a straight line with a slope equal to the reciprocal of 1/2g sin(theta). This may be used to calculate a local value of g."