SOLUTION: For 1989 and 1990 Dave Johnson had the highest decathalon score in the world. When Johnson reached a speed of 32 ft/sec on the pole vault runway, his height above the ground t seco

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: For 1989 and 1990 Dave Johnson had the highest decathalon score in the world. When Johnson reached a speed of 32 ft/sec on the pole vault runway, his height above the ground t seco      Log On


   

Question 90608: For 1989 and 1990 Dave Johnson had the highest decathalon score in the world. When Johnson reached a speed of 32 ft/sec on the pole vault runway, his height above the ground t seconds after leaving the ground was given by h=-16t^2+32t. For how long was he more than 14 ft in the air?
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
14=-16t^2+32t ... 0=-16t^2+32t-14 ... 0=-8t^2+16t-7 ... t=%28-16+%2B-+sqrt%28%28-16%29%5E2-4%28-8%29%28-7%29%29%29%2F%282%28-8%29%29 ... t=%28-16+%2B-+sqrt%2832%29%29%2F-16

t=%281+%2B-+sqrt%282%29%2F4%29 ... he was more than 14 ft in the air between these two times

the difference is sqrt%282%29%2F2 or approx .707 sec