Mark H. answered • 01/21/20

Tutoring in Math and Science at all levels

From the equation and description, we know that he jumped up---i.e. his initial velocity was up. The equation is in the form:

d = -at^{2} / 2 + v_{i }* t + d_{i } , where a is the acceleration of gravity, v_{i }is the initial velocity, and d_{i} is the initial distance the height of the cliff.

So, the initial velocity is 16 ft/sec. a = 32 ft/sec^{2 }, so the time to get to zero velocity is v/a = 0.5 second.

To get the total time, simply set the equation = to zero and solve for t:

-16t^{2} + 16t + 480 = 0

Simplify:

t^{2} - t - 30 = 0 This is factorable, so the rest is easy. You'll get both + and - values for t. Only the + value is significant