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Can somebody please help me with this problem?
April shoots an arrow upward into the air at a speed of feet per second from a platform that is feet high. The height of the arrow is given by the function h(t)-16t^2+64t+29 where t is the time is seconds. What is the maximum height of the arrow?
2 Answers
- ?Lv 72 months ago
h(t) = -16t^2+64t+29
The math way:
Notice that this is a downward Parabola (why?). Therefore it's max is its vertex. So what is the vertex of a parabola?
Thy physics/kinematics way:
Given your height as a function of time, what is its velocity as a function of time?
The max height occurs when it's velocity is zero. So just set v(t) = 0 and you find the time. Replace this time into your height function.
Done!
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- llafferLv 72 months ago
You are given the equation:
h(t) = -16t² + 64t + 29
And asked to find the maximum height.
Since this is college algebra, I'll show you how this can be done without using calculus. You want to get this into vertex form:
h(t) = a(t - h)² + k
The vertex is the point (h, k) which tells you the time it takes to get to the maximum (h) and what the maximum height is (k), which is what you are being asked for.
To do that we need to get the right side to be in the form of (t² + bt). We will subtract 29 from both sides then divide both sides by -16:
h(t) = -16t² + 64t + 29
h(t) - 29 = -16t² + 64t
-[h(t) - 29] / 16 = t² - 4t
Now we complete the square by adding 4 to both sides:
-[h(t) - 29] / 16 + 4 = t² - 4t + 4
The right side can now be factored:
-[h(t) - 29] / 16 + 4 = (t - 2)²
Solve for h(t) again. Subtract 4 from both sides multiply both sides by -16, then add 29 to both sides:
-[h(t) - 29] / 16 = (t - 2)² - 4
h(t) - 29 = -16(t - 2)² + 64
h(t) = -16(t - 2)² + 93
The maximum height is 93 feet reached at 2 seconds after the arrow's launch.