Math Problem Statement
A ball is launched at 42 feet per second. The height of the ball (in feet) is given by the equation h=-16t^2+48t+6, where t is the time (in seconds) since the ball was launched. For how many seconds was the ball at or above a height of 38 feet?
Solution
To find the time the ball is at or above a height of 38 feet, we start with the equation for the height of the ball:
We need to set this equation greater than or equal to 38:
Rearranging gives:
Dividing the entire inequality by -16 (remembering to flip the inequality sign):
Next, we factor the quadratic:
Now, we determine the intervals where this inequality holds. The roots are and . We test the intervals around these points:
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Interval : Choose :
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Interval : Choose :
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Interval : Choose :
The inequality holds for:
Thus, the ball is at or above a height of 38 feet from second to seconds.
Duration
The duration for which the ball is at or above 38 feet is:
Summary
The ball is at or above a height of 38 feet for 1 second.
Would you like further details or explanations? Here are some related questions:
- What are the maximum height and time at which it occurs?
- How does the ball's height change after 2 seconds?
- What would happen if the launch speed were increased?
- How would you graph the height function?
- What is the total time the ball is in the air?
Tip: Always check the endpoints of your intervals when solving inequalities.
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Math Problem Analysis
Mathematical Concepts
Algebra
Quadratic Functions
Inequalities
Formulas
h = -16t^2 + 48t + 6
Quadratic inequality
Theorems
Factoring quadratics
Inequality testing
Suitable Grade Level
Grades 8-10