Time until a stone hits the ground :t=8s. Initial velocity of the stone:vi=0m/s. We have to calculate the height of the ledge. Formula for this is: h=vi * t + g*t^2*2, where g=9.81 m/s^2. h=g*t^2/2. h=9.81 m/s^2*(8s)^2/2, h=9.81 m/s^2*64 s^2/2, h=9.81*32m, h=313.92 m. Answer: The ledge is 313.92 m tall.
