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Let \(s(t)=5 t^{2}-22 t\) be the position function of a particle moving along a coordinate line, where \(s\) is in feet and \(t\) is in seconds. (a) Find the maximum speed of the particle during the time interval \(1 \leq t \leq 3\). (b) When, during the time interval \(1 \leq t \leq 3\), is the parti. cle farthest from the origin? What is its position at tha instant?

Short Answer

Expert verified
(a) Maximum speed is 12 ft/s. (b) The particle is farthest from the origin at \(t=1\) with position \(-17\).

Step by step solution

01

Find the velocity function

The velocity of the particle is the derivative of the position function with respect to time. Given the position function \(s(t) = 5t^2 - 22t\), we differentiate to find the velocity: \[v(t) = \frac{ds}{dt} = \frac{d}{dt}(5t^2 - 22t) = 10t - 22\]
02

Determine critical points of velocity

To find the maximum speed, locate the critical points of the velocity function. Set the derivative equal to zero to solve for \(t\): \[10t - 22 = 0\]\[t = 2.2\]We examine the critical point and endpoints of the interval \([1, 3]\), at \(t = 1, 2.2, 3\).
03

Evaluate velocity at critical and endpoint times

Calculate the velocity at \(t = 1, t = 2.2,\) and \(t = 3\):\(v(1) = 10(1) - 22 = -12\)\(v(2.2) = 10(2.2) - 22 = 0\)\(v(3) = 10(3) - 22 = 8\)The maximum speed is the greatest absolute value, which is \(\max(|-12|, |0|, |8|) = 12\).
04

Understand particle position behavior

To find when the particle is farthest from the origin, consider the position function. We will evaluate the position at the critical time from velocity and the endpoints of the interval.
05

Evaluate position at relevant times

Calculate the position at \(t = 1, t = 2.2,\) and \(t = 3\):\(s(1) = 5(1)^2 - 22(1) = -17\)\(s(2.2) = 5(2.2)^2 - 22(2.2) = -14.2\)\(s(3) = 5(3)^2 - 22(3) = -3\)The farthest from the origin is the greatest distance from zero, which is at \(t = 1\) with \(s(1) = -17\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Velocity Function
In calculus, the velocity function gives us insight into how the position of an object changes over time. It is essentially the derivative of the position function. This means the velocity function represents the rate of change of position with respect to time. For our example, the position function was given as \(s(t) = 5t^2 - 22t\). By finding the derivative of this function, we uncover the velocity function.
  • The derivative process involves differentiating the polynomial: \( \frac{d}{dt}(5t^2 - 22t) = 10t - 22 \).
  • This resulting expression, \(v(t) = 10t - 22\), tells us how fast the position is changing at any given time \(t\).
From this, we can discern key behaviors of the motion. For example, to find when the velocity is zero, which indicates a potential stop or direction change, we set \(v(t) = 0\). Solving for \(t\) here provides critical points for further analysis.
Understood as the body's speed and direction, a positive velocity indicates forward motion, while a negative velocity indicates backward motion.
Position Function
The position function describes the location of a particle along a coordinate line at any time \(t\). It provides a precise mathematical way to track movement over time. Given as \(s(t) = 5t^2 - 22t\), this function helps us see how far a particle is from the origin either at any specific time or over an interval.
  • The structure of the polynomial indicates the path of movement, delineated as squaring the time term affects the curvature, showing non-linear motion.
  • Negative values of \(s(t)\) imply that the particle is on the opposite side of the origin on the coordinate line.
To analyze motion, evaluate the position at specific times. For example, at \(t = 1, 2.2, 3\), we can calculate:
  • \(s(1) = -17\), indicating the position at \(t=1\), which is 17 feet behind the origin.
  • \(s(2.2) = -14.2\), slightly closer to the origin than at \(t=1\).
  • \(s(3) = -3\), the closest to the origin within the given time frame presented.
Utilizing these evaluations helps determine how far the particle stretches from the starting point.
Derivative
A fundamental concept in calculus, the derivative, is a tool that measures how a function changes as its input changes. In the context of motion, as seen in our exercise, the derivative allows us to find both the velocity function from the position function and to further explore dynamics such as speed and acceleration.
  • The derivative of a function provides the slope of the function's graph at any point, offering insight into the rate of change.
  • For a position function, its derivative tells us the velocity because it quantifies how the position changes per unit time: \(v(t) = \frac{ds}{dt}\).
Taking the derivative of \(s(t) = 5t^2 - 22t\) gave us \(v(t) = 10t - 22\).
Derivatives are crucial in predicting future behavior, understanding trends, and optimizing scenarios such as determining maximum speed.
This way, we analyze when the velocity—and thus the particle's movement—reaches critical points by setting the derivative to zero, identifying time points where significant changes in speed or direction occur.

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Most popular questions from this chapter

(a) Show that if \(f\) and \(g\) are functions for which $$ f^{\prime}(x)=g(x) \text { and } g^{\prime}(x)=f(x) $$ for all \(x\), then \(f^{2}(x)-g^{2}(x)\) is a constant. (b) Show that the function \(f(x)=\frac{1}{2}\left(e^{x}+e^{-x}\right)\) and the function \(g(x)=\frac{1}{2}\left(e^{x}-e^{-x}\right)\) have this property.

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