Question

If an object is propelled upward from a height of s feet at an initial veloc​ity of v feet per second, then its height h after t seconds is given by the equation h= -16^2+vt+s, where h is in feet. If the object is propelled from a height of 12 feet with an initial velocity of 96 feet per second its height h is given by the equation h= -16t^2 +96t+12. After how many seconds is the height 120 feet?

Answer 1

That would be obtained by substituting h = 120 and solving :-

-16t^2 + 96t + 12 = 120
-16T^2 + 96t - 108 = 0

solving gives t = 1.5 and t = 4.5

so after propulsion it takes 1.5 seconds to reach 120 feet.