SOLUTION: If a rock falls from a height of 20 meters on Earth, the height H (in meters) after x seconds is approximately H(x) = 20 - 4.9x2. When does the rock strike the ground? Round to t

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Question 431953: If a rock falls from a height of 20 meters on Earth, the height H (in meters) after x seconds is approximately
H(x) = 20 - 4.9x2.
When does the rock strike the ground? Round to the nearest hundredth, if necessary.
A. 4.08 sec
B. 0.91 sec
C. 0.83 sec
D. 2.02 sec


Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi

H(x) = 20 - 4.9x^2   |Height H (in meters) after x seconds

When does the rock strike the ground? 

 0 = 20 -4.9x^2

 20/4.9 = x^2

   x = 2.02sec