SOLUTION: An object is thrown upward at a speed of 77 feet per second by a machine from a height of 7 feet off the ground. The height h of the object after t seconds can be found using the e

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: An object is thrown upward at a speed of 77 feet per second by a machine from a height of 7 feet off the ground. The height h of the object after t seconds can be found using the e      Log On


   

Question 1100672: An object is thrown upward at a speed of 77 feet per second by a machine from a height of 7 feet off the ground. The height h of the object after t seconds can be found using the equation h = -16t^2+77t+7.
When will the height be 62 feet?
When will the object reach ground?
Answer by ikleyn(52777) About Me  (Show Source):
You can put this solution on YOUR website!
.
1)  When will the height be 62 feet?

    Solve the equation h(t) = 62,  which is  -16t^2+77t+7 = 62.


    Find its roots (if they exist).  



2)  When will the object reach ground?

    It will happen when h(t) = 0,  or, which is the same, when

    -16t^2+77t+7 = 0.


    Solve this quadratic eq-n and use its positive root.