1. The problem statement, all variables and given/known data The acceleration of gravity can be measured by project a body upward and measuring the time that it takes to pass two given points in both directions. Show that if the time the body takes to pass a horizontal line A in both directions is Ta and the time to go by a second line B in both directions is Tb then assuming that the acceleration is constant, its magnitude is g = 8h/(Ta^2-Tb^2) 2. Relevant equations y = y0 + 1/2 g t^2 + vot 3. The attempt at a solution There is a diagram where A is the lower position and B is the higher position, they are separated by a distance h. I found Ta = -2/g vy and Tb = -vy +- sqrt(vy^2 - 2gh) but I really don't know where to go after this... If I want acceleration a = dv/dt and v = dx/dt but I'm not quite sure what to do next... If I say delta T = Ta - Tb but that's all i can get.