Table of contents
- 0. Functions7h 52m
- Introduction to Functions16m
- Piecewise Functions10m
- Properties of Functions9m
- Common Functions1h 8m
- Transformations5m
- Combining Functions27m
- Exponent rules32m
- Exponential Functions28m
- Logarithmic Functions24m
- Properties of Logarithms34m
- Exponential & Logarithmic Equations35m
- Introduction to Trigonometric Functions38m
- Graphs of Trigonometric Functions44m
- Trigonometric Identities47m
- Inverse Trigonometric Functions48m
- 1. Limits and Continuity2h 2m
- 2. Intro to Derivatives1h 33m
- 3. Techniques of Differentiation3h 18m
- 4. Applications of Derivatives2h 38m
- 5. Graphical Applications of Derivatives6h 2m
- 6. Derivatives of Inverse, Exponential, & Logarithmic Functions2h 37m
- 7. Antiderivatives & Indefinite Integrals1h 26m
- 8. Definite Integrals4h 44m
- 9. Graphical Applications of Integrals2h 27m
- 10. Physics Applications of Integrals 2h 22m
4. Applications of Derivatives
Motion Analysis
Problem 3.6.12d
Textbook Question
Airline travel The following figure shows the position function of an airliner on an out-and-back trip from Seattle to Minneapolis, where s = f(t) is the number of ground miles from Seattle t hours after take-off at 6:00 A.M. The plane returns to Seattle 8.5 hours later at 2:30 P.M. <IMAGE>
d. Determine the velocity of the airliner at noon (t = 6) and explain why the velocity is negative.

1
To determine the velocity of the airliner at noon (t = 6), we need to find the derivative of the position function s = f(t) with respect to time t. The derivative, f'(t), represents the velocity of the airliner at any given time t.
Evaluate the derivative f'(t) at t = 6 to find the velocity at noon. This involves substituting t = 6 into the derivative function f'(t).
The velocity is negative because the airliner is on its return trip to Seattle. A negative velocity indicates that the direction of travel is towards the starting point, which in this case is Seattle.
Conceptually, velocity is a vector quantity, meaning it has both magnitude and direction. A negative value signifies movement in the opposite direction to the positive axis, which is typically defined as the direction away from the starting point.
Ensure that the units of the velocity are consistent with the units used in the position function. If the position function is in miles, the velocity will be in miles per hour.

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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, denoted as s = f(t), describes the location of an object over time. In this context, it represents the distance of the airliner from Seattle as a function of time since take-off. Understanding this function is crucial for analyzing the motion of the airliner, as it provides the necessary data to determine both velocity and acceleration.
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Velocity
Velocity is defined as the rate of change of position with respect to time, mathematically expressed as v(t) = f'(t). It indicates both the speed and direction of an object's movement. In this scenario, calculating the velocity at a specific time, such as noon (t = 6), helps to understand how fast the airliner is traveling and in which direction relative to Seattle.
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Negative Velocity
A negative velocity indicates that the object is moving in the opposite direction to the defined positive direction, which in this case is towards Seattle. When the airliner is returning to Seattle after reaching Minneapolis, its velocity becomes negative. This concept is essential for interpreting the motion of the airliner and understanding the implications of its position function at different times.
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