Question

A boy standing on a 64-foot cliff drops a coin off the cliff. If the equation of the height, h, of the coin, t, seconds after it drops is h = -16t2 + 64, about how many seconds will the coin take to reach the bottom of the cliff?

Answer 1

The height at the bottom of the cliff will be 0. So we substitute 0 for h and solve for t.\[0=-16t^2+64\]\[-16t^2=-64\]\[t^2=4\]\[t=\pm 2\]Because we are analyzing time, the negative value can be disregarded. The time it takes for it to reach the bottom will be 2 seconds.