Answer:
187.5 seconds
Explanation:
The initial speed of the bullet is 3000 ft/s, so v = 3000.
At first, the bullet is at ground level, so h = 0.
The bullet is fired up, goes up to a maximums height, and then starts falling until it reaches ground level again at h = 0.
h = vt - 16t²
0 = 3000t - 16t²
16t² - 3000t = 0
8t(2t - 375) = 0
8t = 0 or 2t - 375 = 0
t = 0 or 2t = 375
t = 0 or t = 375/2 = 187.5
The height of the bullet is 0 ft at t = 0 seconds (when it is fired) and at t = 187.5 seconds when if falls on the ground.
Answer: 187.5 seconds