Question

A firecracker shoots up from a hill 145 feet high with an initial speed of 80 feet per second. Using the formula H(t) = -16t2 + vt + s, approximately how long will it take the firecracker to hit the ground?

a. 13 seconds b. 11 seconds c. 9 seconds d. 6 seconds

Answer 1

ITs not 13...test says Wrong...Its Approx 6 sec or D.

Answer 2

we are given the formula H(t) = -16t2 + vt + s where s is the initial height in feet, v is speed in feet per second. Substituting the given data, 0 = -16t2 + 80t + 145. t is equal to 6.4131 seconds which is the time to reach the maximum height. hence, the total time is 6.4131*2 equal to 12.83 seconds or A. 13 seconds