SOLUTION: Write a quadratic equation and solve. Assume that air resistance is negligible. A construction worker dropped a bolt from the twelfth floor, a height of 120 ft. How long (to the

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equation Customizable Word Problems -> SOLUTION: Write a quadratic equation and solve. Assume that air resistance is negligible. A construction worker dropped a bolt from the twelfth floor, a height of 120 ft. How long (to the      Log On


   

Question 1028179: Write a quadratic equation and solve. Assume that air resistance is negligible.
A construction worker dropped a bolt from the twelfth floor, a height of 120 ft. How long (to the nearest tenth of a second) did it take to reach the ground?

FORMULA: h(t) = -16t^2 + h
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
What is the height when +t+=+0+ ?
That is the instant when the bolt is dropped?
+h%280%29+=+-16%2A0%5E2+%2B+h+
+h%280%29+=+h+
You are told that this height is +120+ ft above ground
+h%280%29+=+120+
+h+=+120+
So, now the equation is:
+h%28t%29+=+-16t%5E2+%2B+120+
------------------------
Now you want to find +t+ when +h%28t%29+=+0+
+0+=+-16t%5E2+%2B+120+
+16t%5E2+=+120+
+t%5E2+=+15%2F2+
+t+=+sqrt%28+7.5+%29+
+t+=+2.7386+
The bolt takes 2.7386 sec to reach the ground