An object was thrown upward from the top of an 80ft tower. The height h of the object after t seconds is represented by the quadratic equation h=-16t^2 + 64t + 80. After how many seconds will the object hit the ground?
Accepted Solution
A:
The problem gives you: h=-16t^2+64t+80 where h is height in feet t is time in secs
If it hits the ground, h = 0 so set h=0 and solve for t: h=-16t^2+64t+80 0=-16t^2+64t+80 0=-4t^2+16t+5 Solving using the quadratic equation yields: t = {-0.29, 4.29} We can throw out the negative solution leaving t = 4.29 seconds