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9 | 9 | "\n", |
10 | 10 | "## Linear Rate of Change\n", |
11 | 11 | "\n", |
12 | | - "For example, imagine a function that returns the number of meters travelled by a cyclist based on the number of seconds that the cyclist has been cycling.\n", |
| 12 | + "For example, imagine a function that returns the number of meters traveled by a cyclist based on the number of seconds that the cyclist has been cycling.\n", |
13 | 13 | "\n", |
14 | 14 | "Here is such a function:\n", |
15 | 15 | "\n", |
|
60 | 60 | "cell_type": "markdown", |
61 | 61 | "metadata": {}, |
62 | 62 | "source": [ |
63 | | - "It's clear from the graph that ***q*** is a *linear* function that describes a slope in which distance increases at a constant rate over time. In other words, the cyclist is travelling at a constant speed.\n", |
| 63 | + "It's clear from the graph that ***q*** is a *linear* function that describes a slope in which distance increases at a constant rate over time. In other words, the cyclist is traveling at a constant speed.\n", |
64 | 64 | "\n", |
65 | 65 | "But what speed?\n", |
66 | 66 | "\n", |
67 | | - "Speed, or more technically, velocity is a measure of change - it measures how the distance travelled changes over time (which is why we typically express it as a unit of distance per a unit of time, like *miles-per-hour* or *meters-per-second*). So we're looking for a way to measure the change in the line created by the function.\n", |
| 67 | + "Speed, or more technically, velocity is a measure of change - it measures how the distance traveled changes over time (which is why we typically express it as a unit of distance per a unit of time, like *miles-per-hour* or *meters-per-second*). So we're looking for a way to measure the change in the line created by the function.\n", |
68 | 68 | "\n", |
69 | 69 | "The change in values along the line define its *slope*, which we know from a previous lesson is represented like this:\n", |
70 | 70 | "\n", |
|
79 | 79 | "- After 1 second, ***x*** is 1 and ***q***(1) = **3**.\n", |
80 | 80 | "- After 10 seconds, ***x*** is 10 and ***q***(10) = 21.\n", |
81 | 81 | "\n", |
82 | | - "So we can meassure the rate of change like this:\n", |
| 82 | + "So we can measure the rate of change like this:\n", |
83 | 83 | "\n", |
84 | 84 | "\\begin{equation}m = \\frac{21 - 3}{10 - 1} \\end{equation}\n", |
85 | 85 | "\n", |
|
91 | 91 | "\n", |
92 | 92 | "\\begin{equation}m = \\frac{2}{1} \\end{equation}\n", |
93 | 93 | "\n", |
94 | | - "So our rate of change is <sup>2</sup>/<sub>1</sub> or put another way, the cyclist is travelling at 2 meters-per-second." |
| 94 | + "So our rate of change is <sup>2</sup>/<sub>1</sub> or put another way, the cyclist is traveling at 2 meters-per-second." |
95 | 95 | ] |
96 | 96 | }, |
97 | 97 | { |
98 | 98 | "cell_type": "markdown", |
99 | 99 | "metadata": {}, |
100 | 100 | "source": [ |
101 | 101 | "## Average Rate of Change\n", |
102 | | - "OK, let's look at another function that calculates distance travelled for a given number of seconds:\n", |
| 102 | + "OK, let's look at another function that calculates distance traveled for a given number of seconds:\n", |
103 | 103 | "\n", |
104 | 104 | "\\begin{equation}r(x) = x^{2} + x\\end{equation}\n", |
105 | 105 | "\n", |
|
150 | 150 | "source": [ |
151 | 151 | "This time, the function is not linear. It's actually a quadratic function, and the line from 0 seconds to 10 seconds shows an exponential increase; in other words, the cyclist is *accelerating*.\n", |
152 | 152 | "\n", |
153 | | - "Technically, acceleration itself is a measure of change in velocity over time; and velocity, as we've already discussed, is a measure of change in distance over time. So measuring accelleration is pretty complex, and requires *differential calculus*, which we're going to cover shortly. In fact, even just measuring the velocity at a single point in time requires differential calculus; but we can use algebraic methods to calculate an *average* rate of velocity for a given period shown in the graph.\n", |
| 153 | + "Technically, acceleration itself is a measure of change in velocity over time; and velocity, as we've already discussed, is a measure of change in distance over time. So measuring acceleration is pretty complex, and requires *differential calculus*, which we're going to cover shortly. In fact, even just measuring the velocity at a single point in time requires differential calculus; but we can use algebraic methods to calculate an *average* rate of velocity for a given period shown in the graph.\n", |
154 | 154 | "\n", |
155 | 155 | "First, we need to define a *secant* line that joins two points in our exponential arc to create a straight slope. For example, a secant line for the entire 10 second time span would join the following two points:\n", |
156 | 156 | "\n", |
|
164 | 164 | "cell_type": "code", |
165 | 165 | "execution_count": 12, |
166 | 166 | "metadata": { |
167 | | - "scrolled": true |
| 167 | + "scrolled": false |
168 | 168 | }, |
169 | 169 | "outputs": [ |
170 | 170 | { |
|
215 | 215 | "- At 0 seconds, ***x*** is 0 and ***r***(0) = **0**.\n", |
216 | 216 | "- At 10 seconds, ***x*** is 10 and ***r***(10) = 110.\n", |
217 | 217 | "\n", |
218 | | - "So we can meassure the rate of change like this:\n", |
| 218 | + "So we can measure the rate of change like this:\n", |
219 | 219 | "\n", |
220 | 220 | "\\begin{equation}m = \\frac{110 - 0}{10 - 0} \\end{equation}\n", |
221 | 221 | "\n", |
|
227 | 227 | "\n", |
228 | 228 | "\\begin{equation}m = \\frac{11}{1} \\end{equation}\n", |
229 | 229 | "\n", |
230 | | - "So our rate of change is <sup>11</sup>/<sub>1</sub> or put another way, the cyclist is travelling at an average velocity of 11 meters-per-second over the 10-second period.\n", |
| 230 | + "So our rate of change is <sup>11</sup>/<sub>1</sub> or put another way, the cyclist is traveling at an average velocity of 11 meters-per-second over the 10-second period.\n", |
231 | 231 | "\n", |
232 | 232 | "Of course, we can measure the average velocity between any two points on the exponential line. Use the following R code to show the secant line for the period between 2 and 7 seconds, and calculate the average velocity for that period" |
233 | 233 | ] |
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