When will the object hit the ground after it is launched? Explain how you found your answer

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.

Answer 1

Since we want to know how much time elapsed since the object was launched until it ht the ground. At the ground, the height is 0.

 

Therefore the equation  h(t) = 80t – 16t² becomes 0= 80t – 16t²

 

Solving the equation for t gives  80t =16t² or 16t=80 or t=5sec

 

The object hits the ground 5 seconds after it is launched.