1. The problem statement, all variables and given/known data To find the height of a cliff, you drop a rock from the top and 10s ater, you hear the sound of it hitting the ground at the foot of the cliff. Ignoring air resistance, how high is the cliff if the speed of sound is 330m/s. 2. Relevant equations Xf = Xo = VoT + 1/2aT^2 Vf = Vo + aT Vf^2 = Vo^2 + 2a(deltaX) V = (deltaX)/(deltaT) maybe? 3. The attempt at a solution ok so here is what i tried. i drew it so that T1 = time for rock to fall T2 = time for sound to go back Tt = Total time = 10s so T1+T2 = Tt = 10s then I did Vs = velocity of sound, so Vs = deltaX / deltaT solved for deltaX which = height of the cliff and got deltaX = Vs(Tt-T1) then for the rock, Vf^2 = Vo^2 +2a(deltaX) knowing that Vo^2 = 0, and a = g, and solving for deltaX deltaX = Vf^2/2g since both equations are solving for the same deltaX, I set them equal to eachother Vs(Tt-T1) = Vf^2/2g the unknowns are T1, and Vf I feel pretty good up to this point, then i'm not so sure, but next i tried... to solve for T2 by Vf = Vo +at t is for the rock so... Vf = g(Tt-T2) then plug that in and get the equation Vs(Tt-T1) = g(Tt-T2)^2/2g but there's still two unknowns with T1 and T2, so... if (Tt-T2) = T1, can i plug that in on the right side, so that T1 is the only variable? it's just on both sides? am i close? where did i mess up?