Question

If an object is propelled upward from ground level with initial velocity of 55 feet per second, it's height h in feet t seconds later is given by the equation H=-16t^2+55t. after how many seconds does the object hit ground?

Answer 1

V = Vo + g*Tr = 0 @ max Ht.
Tr = -Vo/g = -55/-32 = 1.72 s. = Rise time.

Tf = Tr = 1.72 s. = Fall time.

Tr+Tf = 1.72 + 1.72 = 3.44 s. To hit gnd