SOLUTION: A ball is thrown straight upward from the ground. Its height above the ground in meters after t seconds is given by -4.9t^2+30t+c 1. Find the value for the constant c. 2. Find

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: A ball is thrown straight upward from the ground. Its height above the ground in meters after t seconds is given by -4.9t^2+30t+c 1. Find the value for the constant c. 2. Find      Log On


   

Question 936959: A ball is thrown straight upward from the ground. Its height above the ground in meters after t seconds is given by -4.9t^2+30t+c
1. Find the value for the constant c.
2. Find the values of t that make the height zero and give a practical interpretation of each value.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+h%28t%29+=+-4.9t%5E2+%2B+30t+%2B+c+
The ball is thrown from the ground, so
that tells me:
+h%280%29+=+0+
+h%290%29+=+-4.9%2A0%5E2+%2B+30%2A0+%2B+c+
+0+=+0+%2B+0+%2B+c+
+c=+0+
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+h%28t%29+=+0+
I already know that +h%280%29+=+0+
+0+=+-4.9t%5E2+%2B+30t+%2B+0+
+-4.9t%5E2+%2B+30t+=+0+
+t%2A%28+-4.9t+%2B+30+%29+=+0+
+-4.9t+%2B+30+=+0+
+4.9t+=+30+
+t+=+6.122+
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+t+=+0+ is when ball is trown upward
+t+=+6.122+sec is when th ball lands
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Here's the plot:
+graph%28+400%2C+400%2C+-1%2C+7%2C+-5%2C+50%2C+-4.9x%5E2+%2B+30x+%29+