Question

A timer is started and a few moments later a model airplane is launched from the ground. Its height (in feet) as a function of time (in seconds after the timer was started) is given by the equation h(t)=−(t−12)2+81
. Which of the following statements is true?

The airplane reaches its minimum height of 12 feet in 81 seconds.
The airplane reaches its maximum height of 81 feet in 12 seconds.
The airplane reaches its minimum height of 81 feet in 12 seconds.

The airplane reaches its maximum height of 12 feet in 81 seconds.

Answer 1

The airplane reaches its maximum height of 81 feet in 12 seconds.

Behavior of curves

If y = $x^{2}$, it means that the second derivate is 2 which is positive, then there is a minimum turning point.

If y = - $x^{2}$, it means that the second derivative will be -2 which is negative, then there is a maximum turning point.

Analysis:

h(t) = -$(t - 12)^{2}$ + 81

By expanding,

h(t) = -($t^{2}$ - 24t + 144) +81

h(t) = -$t^{2}$ + 24t - 144 + 81

h(t) = -$t^{2}$ + 24t - 63

at turning point d/dt(h(t)) = 0

d/dt (h(t)) = -2t +24

-2t +24 = 0

if we differentiate again, second derivative is -2 which is negative, so it is a maximum point.

2t = 24

t  = 12 seconds

h(t) at t = 12

h(t) = $-(12)^{2}$ + 24(12) - 63 = 81 feet

In conclusion, the maximum height of the airplane after 12 seconds is 81 feet.

Learn more about minimum and maximum points: brainly.com/question/14993153

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