A rocket is launched from atop a 54-foot cliff with an initial velocity of 119 feet per second. The height of the rocket t seconds after launch is given by the equation h = –16t 2 + 119t + 54. Graph the equation to find out how long after the rocket is launched it will hit the ground. Estimate your answer to the nearest hundredth of a second.

Question

campbell_st · Answer

well to hit the ground, the height = 0

so you have 

$$0 = -16t^2 + 119t + 54$$

use the general quadratic formula to find t. 

and only use the positive t value in your answer

anonymous · Answer

i dont know the quadratic formula well

campbell_st · Answer

ok... its 

$$t = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$

you have a = -16, b = 119 and c = 54

substitute the values and calculate the values of t. 

only use the positive value

hope it helps