SOLUTION: Baseball Tonisha hit a baseball into the air with an initial upward velocity of 48 feet per second. The height h in feet of the ball above the ground can be modeled by h= - 16

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Baseball Tonisha hit a baseball into the air with an initial upward velocity of 48 feet per second. The height h in feet of the ball above the ground can be modeled by h= - 16      Log On


   

Question 118894:
Baseball Tonisha hit a baseball into the air with an initial upward velocity of 48 feet per second. The height h in feet of the ball above the ground can be modeled by h= - 16t2 + 48t + 2, is the time in seconds after Tonisha hit the baseball. Find the time it takes the ball to reach 38 feet above the ground.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
h=+-+16t%5E2+%2B+48t+%2B+2 Start with the given equation


38=+-+16t%5E2+%2B+48t+%2B+2 Plug in h=38


0=-16t%5E2%2B48t%2B2-38 Subtract 38 from both sides.


0=-16t%5E2%2B48t-36 Combine like terms


0=-4%282t-3%29%282t-3%29 Factor the right side


Now set each factor equal to zero:
2t-3=0 or 2t-3=0

t=3%2F2 or t=3%2F2 Now solve for t in each case


Since we have a repeating answer, our only answer is t=3%2F2 (which is t=1.5 in decimal form)

Notice if we graph y=-16t%5E2%2B48t-36 we can see that the only root is t=3%2F2. So this visually verifies our answer.


+graph%28500%2C500%2C-10%2C10%2C-10%2C10%2C0%2C+-16x%5E2%2B48x-36%29+




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Answer:
So it takes 1.5 seconds for the ball to reach 38 above the ground