Question

An object is launched from the ground. The object’s height, in feet, can be described by the quadratic function h(t) = 80t – 16t2, where t is the time, in seconds, since the object was launched. When will the object hit the ground after it is launched? Explain how you found your answer.

Answer 1

Set h(t), time = 0.
0 = 80t-16t^2
-16t^2+80t =0

Factor
-16t(t-5) =0

t =0 (when launched)
& t = 5

Answer 2

Sample Response: The object will hit the ground after 5 seconds. You can rewrite the quadratic function as a quadratic equation set equal to zero to find the zeros of the function 0 = –16t2 + 80t + 0. You can factor or use the quadratic formula to get t = 0 and t = 5. Therefore, it is on the ground at t = 0 (time of launch) and then hits the ground at t = 5 seconds

What did you include in your response? Check all that apply.

I Rewrite the quadratic function as a quadratic equation set equal to zero: 0 = –16t2 + 80t + 0.

Use the quadratic formula to solve for the zeros.

Factor to solve for the zeros.

t = 0 and t = 5 seconds.

The object will hit the ground after 5 seconds.