Question

An object is launched straight up into the air with an initial velocity of 40 meters per second, from a height 30 m above the ground. How many seconds later will the object hit the ground?

Enter your answer as a number rounded to the nearest tenth, such as: 42.5

Answer 1

8.8 seconds

Explanation:

Taking g = 9.81 m/s²

Convention: downwards positive

30 = -40t + 0.5(9.81)t²

4.905t² - 40t - 30 = 0

t = 8.846327763, -0.6913838279

t = 8.8s