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Ch. 4 - Applications of the Derivative
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 4, Problem 4.1.71

Suppose the position of an object moving horizontally after seconds is given by the function s(t) = 32t - t⁴, where 0 ≤ t ≤ 3 and s is measured in feet, with s > 0 corresponding to positions to the right of the origin. When is the object farthest to the right?

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1
To find when the object is farthest to the right, we need to determine the maximum value of the position function s(t) = 32t - t^4 over the interval 0 ≤ t ≤ 3.
First, find the derivative of the position function, s'(t), to determine the critical points. The derivative is s'(t) = 32 - 4t^3.
Set the derivative equal to zero to find the critical points: 32 - 4t^3 = 0. Solve for t to find the critical points.
Evaluate the position function s(t) at the critical points and at the endpoints of the interval, t = 0 and t = 3, to determine which gives the maximum value.
Compare the values of s(t) at these points to determine when the object is farthest to the right. The largest value of s(t) will indicate the time when the object is farthest to the right.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Position Function

The position function s(t) describes the location of an object at any given time t. In this case, s(t) = 32t - t⁴ represents the position of an object moving horizontally, where t is measured in seconds and s in feet. Understanding this function is crucial for determining the object's position over time and analyzing its motion.
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Relations and Functions

Critical Points

Critical points occur where the derivative of a function is zero or undefined. To find when the object is farthest to the right, we need to calculate the derivative of the position function, s'(t), and set it equal to zero. This helps identify potential maximum positions within the given interval.
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Critical Points

Second Derivative Test

The second derivative test is a method used to determine the concavity of a function at critical points. By evaluating the second derivative, s''(t), we can ascertain whether a critical point is a local maximum, minimum, or neither. This is essential for confirming that the object is indeed at its farthest right position when the first derivative is zero.
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The Second Derivative Test: Finding Local Extrema