VIDEO TRANSCRIPT

This is Giancoli Answers with Mr. Dychko. When King Kong falls a distance of 380 meters off the Empire State building, he has an initial velocity of 0 meters per second and we'll take down to be positive which gives an acceleration of 9.8 meters per second squared down. Here's the distance formula and it has only one unknown which is t and we'll get rid of this term entirely because the initial speed is zero and then multiply both sides by 2 over a and that gives t squared is 2d over a and then take the square root of both sides giving t is square root of 2d over a. So that's the square root of 2 times 380 meters over 9.8 meters per second squared which is 8.8 seconds until he hits the ground and his speed when that happens will be given by this formula and notice that I'm choosing a formula that does not involve t just because it's nice to not use your own results in subsequent calculations because if there is an error in these 8.8 seconds, that would make your next answer wrong as well. So when possible, try to use formulas that use just the data you are given in the question. So initial speed again is zero and we have the final speed then is a square root of 2 times acceleration times the distance so that's square root of 2 times 9.8 times 380 meters which is 86 meters per second which is quite fast.