Question

A projectile was launched straight up from the ground with an initial velocity of 48 ft/s. The height of the projectile t seconds after launch is modeled by the function f(t)=-16t^2+48t.
How long was the projectile in the air before it hit the ground?

A. 3 seconds
B. 4 seconds
C. 5 seconds
D. 6 seconds

Answer 1

Factor f(t) and you can identify the values of t for which the height is zero.
.. f(t) = -16t(t -3)

The projectile lands after 3 seconds in the air. (selection A)