Assume that a ruler is initially suspended such that its lower end is at height, h = 0. The ruler is then dropped and allowed to accelerate (with constant acceleration a = -g), towards the earth. The ruler is caught by a student when it has dropped a distance, d (i.e. the bottom of the ruler is now at the position, -d). What is the time t it takes for the ruler to fall a distance d? In other words, use:
y (t) = y1 + v1t + 0.5 at2
and the given initial conditions, to find an expression for t in terms of the distance y.