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Calculus: Early Transcendental Functions

Robert T. Smith, Roland B. Minton

Chapter 5

Applications of the Definite Integral - all with Video Answers

Educators


Section 1

Area Between Curves

02:03

Problem 1

Find the area between the curves on the given interval.
$$y=x^{3}, y=x^{2}-1,1 \leq x \leq 3$$

Ernest Castorena
Ernest Castorena
Numerade Educator
01:00

Problem 2

Find the area between the curves on the given interval.
$$y=\cos x, y=x^{2}+2,0 \leq x \leq 2$$

Ernest Castorena
Ernest Castorena
Numerade Educator
01:49

Problem 3

Find the area between the curves on the given interval.
$$y=e^{x}, y=x-1,-2 \leq x \leq 0$$

Ernest Castorena
Ernest Castorena
Numerade Educator
01:22

Problem 4

Find the area between the curves on the given interval.
$$y=e^{-x}, y=x^{2}, 1 \leq x \leq 4$$

Ernest Castorena
Ernest Castorena
Numerade Educator
02:21

Problem 5

Sketch and find the area of the region determined by the intersections of the curves.
$$y=x^{2}-1, y=7-x^{2}$$

Ernest Castorena
Ernest Castorena
Numerade Educator
02:43

Problem 6

Sketch and find the area of the region determined by the intersections of the curves.
$$y=x^{2}-1, y=\frac{1}{2} x^{2}$$

Ernest Castorena
Ernest Castorena
Numerade Educator
02:28

Problem 7

Sketch and find the area of the region determined by the intersections of the curves.
$$y=x^{3}, y=3 x+2$$

Ernest Castorena
Ernest Castorena
Numerade Educator
00:43

Problem 8

Sketch and find the area of the region determined by the intersections of the curves.
$$y=\sqrt{x}, y=x^{2}$$

Ernest Castorena
Ernest Castorena
Numerade Educator
03:14

Problem 9

Sketch and find the area of the region determined by the intersections of the curves.
$$y=4 x e^{-x^{2}}, y=|x|$$

Ernest Castorena
Ernest Castorena
Numerade Educator
03:04

Problem 10

Sketch and find the area of the region determined by the intersections of the curves.
$$y=\frac{2}{x^{2}+1}, y=|x|$$

Ernest Castorena
Ernest Castorena
Numerade Educator
01:50

Problem 11

Sketch and find the area of the region determined by the intersections of the curves.
$$y=\frac{5 x}{x^{2}+1}, y=x$$

Ernest Castorena
Ernest Castorena
Numerade Educator
06:23

Problem 12

Sketch and find the area of the region determined by the intersections of the curves.
$$y=\sin x(0 \leq x \leq 2 \pi), y=\cos x$$

Ernest Castorena
Ernest Castorena
Numerade Educator
01:58

Problem 13

Sketch and estimate the area determined by the intersections of the curves.
$$y=e^{x}, y=1-x^{2}$$

Gregory Higby
Gregory Higby
Numerade Educator
01:49

Problem 14

Sketch and estimate the area determined by the intersections of the curves.
$$y=x^{4}, y=1-x$$

Gregory Higby
Gregory Higby
Numerade Educator
01:44

Problem 15

Sketch and estimate the area determined by the intersections of the curves.
$$y=\sin x, y=x^{2}$$

Gregory Higby
Gregory Higby
Numerade Educator
02:00

Problem 16

Sketch and estimate the area determined by the intersections of the curves.
$$y=\cos x, y=x^{4}$$

Gregory Higby
Gregory Higby
Numerade Educator
01:56

Problem 17

Sketch and estimate the area determined by the intersections of the curves.
$$y=x^{4}, y=2+x$$

Gregory Higby
Gregory Higby
Numerade Educator
01:50

Problem 18

Sketch and estimate the area determined by the intersections of the curves.
$$y=\ln x, y=x^{2}-2$$

Gregory Higby
Gregory Higby
Numerade Educator
02:38

Problem 19

Sketch and find the area of the region bounded by the given curves. Choose the variable of integration so that the area is written as a single integral.
$$y=x, y=2-x, y=0$$

Gregory Higby
Gregory Higby
Numerade Educator
02:26

Problem 20

Sketch and find the area of the region bounded by the given curves. Choose the variable of integration so that the area is written as a single integral.
$$y=2 x(x>0), y=3-x^{2}, x=0$$

Gregory Higby
Gregory Higby
Numerade Educator
01:25

Problem 21

Sketch and find the area of the region bounded by the given curves. Choose the variable of integration so that the area is written as a single integral.
$$x=y, x=-y, x=1$$

Gregory Higby
Gregory Higby
Numerade Educator
04:25

Problem 22

Sketch and find the area of the region bounded by the given curves. Choose the variable of integration so that the area is written as a single integral.
$$x=3 y, x=2+y^{2}$$

Gregory Higby
Gregory Higby
Numerade Educator
02:13

Problem 23

Sketch and find the area of the region bounded by the given curves. Choose the variable of integration so that the area is written as a single integral.
$$y=x, y=2, y=6-x, y=0$$

Gregory Higby
Gregory Higby
Numerade Educator
02:33

Problem 24

Sketch and find the area of the region bounded by the given curves. Choose the variable of integration so that the area is written as a single integral.
$$x=y^{2}, x=4$$

Gregory Higby
Gregory Higby
Numerade Educator
02:09

Problem 25

Sketch and find the area of the region bounded by the given curves. Choose the variable of integration so that the area is written as a single integral.
$$y=e^{x}, y=4 e^{-x}, y=1$$

Gregory Higby
Gregory Higby
Numerade Educator
01:42

Problem 26

Sketch and find the area of the region bounded by the given curves. Choose the variable of integration so that the area is written as a single integral.
$$y=\frac{\ln x}{x}, y=\frac{1-x}{x^{2}+1}, x=4$$

Gregory Higby
Gregory Higby
Numerade Educator
04:37

Problem 27

The average value of a function $f(x)$ on the interval $[a, b]$ is $A=\frac{1}{b-a} \int_{a}^{b} f(x) d x .$ Compute the average value of $f(x)=x^{2}$ on [0,3] and show that the area above $y=A$ and below $y=f(x)$ equals the area below $y=A$ and above $y=f(x)$

Gregory Higby
Gregory Higby
Numerade Educator
04:03

Problem 28

Prove that the result of exercise 27 is always true by showing that $\int_{a}^{b}[f(x)-A] d x=0$

Gregory Higby
Gregory Higby
Numerade Educator
08:05

Problem 29

The United States oil consumption for the years $1970-1974$ was approximately equal to $f(t)=16.1 e^{0.07 t}$ million barrels per year, where $t=0$ corresponds to $1970 .$ Following an oil shortage in $1974,$ the country's consumption changed and was better modeled by $g(t)=21.3 e^{0.04(t-4)}$ million barrels per year, for $t \geq 4 .$ Show that $f(4) \approx g(4)$ and explain what this number represents. Compute the area between $f(t)$ and $g(t)$ for $4 \leq t \leq 10 .$ Use this number to estimate the number of barrels of oil saved by Americans' reduced oil consumption from 1974 to 1980
GRAPH CANT COPY

Uma Kumari
Uma Kumari
Numerade Educator
02:38

Problem 30

Suppose that a nation's fuelwood consumption is given by $76 e^{0.03 t} \mathrm{m}^{3} / \mathrm{yr}$ and new tree growth is $50-6 e^{0.09 t} \mathrm{m}^{3} / \mathrm{yr}$
Compute and interpret the area between the curves for $0 \leq t \leq 10$

Gregory Higby
Gregory Higby
Numerade Educator
02:11

Problem 31

Suppose that the birthrate for a certain population is $b(t)=2 e^{0.04 t}$ million people per year and the death rate for the same population is $d(t)=2 e^{0.02 t}$ million people per year. Show that $b(t) \geq d(t)$ for $t \geq 0$ and explain why the area between the curves represents the increase in population. Compute the increase in population for $0 \leq t \leq 10$

Gregory Higby
Gregory Higby
Numerade Educator
03:22

Problem 32

Suppose that the birthrate for a population is $b(t)=2 e^{0.04 t}$ million people per year and the death rate for the same population is $d(t)=3 e^{0.02 t}$ million people per year. Find the intersection $T$ of the curves $(T>0) .$ Interpret the area between the curves for $0 \leq t \leq T$ and the area between the curves for $T \leq t \leq 30 .$ Compute the net change in population for $0 \leq t \leq 30$

Gregory Higby
Gregory Higby
Numerade Educator
06:48

Problem 33

In collisions between a ball and a striking object (e.g., a baseball bat or tennis racket), the ball changes shape, first compressing and then expanding. If $x$ represents the change in diameter of the ball (e.g., in inches) for $0 \leq x \leq m$ and $f(x)$ represents the force between the ball and striking object (e.g., in pounds), then the area under the curve $y=f(x)$ is proportional to the energy transferred. Suppose that $f_{c}(x)$ is the force during compression and $f_{e}(x)$ is the force during expansion. Explain why $\int_{0}^{m}\left[f_{c}(x)-f_{e}(x)\right] d x$ is proportional to the energy lost by the ball (due to friction) and thus $\int_{0}^{m}\left[f_{c}(x)-f_{e}(x)\right] d x / \int_{0}^{m} f_{c}(x) d x$ is the proportion of energy
lost in the collision. For a baseball and bat, reasonable values are shown (see Adair's book The Physics of Baseball):$$\begin{array}{|c|c|c|c|c|c|}
\hline x \text { (in.) } & 0 & 0.1 & 0.2 & 0.3 & 0.4 \\\hline f_{c}(x)(\mathrm{lb}) & 0 & 250 & 600 & 1200 & 1750 \\\hline f_{e}(x)(\mathrm{lb}) & 0 & 10 & 100 & 270 & 1750 \\\hline\end{array}$$ Use Simpson's Rule to estimate the proportion of energy retained by the baseball.

Eric Mockensturm
Eric Mockensturm
Numerade Educator
05:05

Problem 34

Using the same notation as in exercise $33,$ values for the force $f_{c}(x)$ during compression and force $f_{e}(x)$ during expansion of a golf ball are given by $$\begin{array}{|l|l|l|l|l|l|}
\hline x \text { (in.) } & 0 & 0.045 & 0.09 & 0.135 & 0.18 \\\hline f_{c}(x)(\mathrm{lb}) & 0 & 200 & 500 & 1000 & 1800 \\\hline f_{e}(x)(\mathrm{lb}) & 0 & 125 & 350 & 700 & 1800 \\\hline\end{array}$$ Use Simpson's Rule to estimate the proportion of energy retained by the golf ball.

Keshav Singh
Keshav Singh
Numerade Educator
02:37

Problem 35

Much like the compression and expansion of a ball discussed in exercises 33 and $34,$ the force exerted by a tendon as a function of its extension determines the loss of energy (see the chapter introduction). Suppose that $x$ is the extension of the tendon, $f_{s}(x)$ is the force during stretching of the tendon and $f_{r}(x)$ is the force during recoil of the tendon. The data given are for a hind leg tendon of a wallaby (see Alexander's book Exploring Biomechanics): $$\begin{array}{|l|l|l|l|l|l|}
\hline x(\mathrm{mm}) & 0 & 0.75 & 1.5 & 2.25 & 3.0 \\\hline f_{s}(x)(\mathrm{N}) & 0 & 110 & 250 & 450 & 700 \\\hline f_{r}(x)(\mathrm{N}) & 0 & 100 & 230 & 410 & 700 \\\hline\end{array}$$ Use Simpson's Rule to estimate the proportion of energy returned by the tendon.

Prabhu Ramji
Prabhu Ramji
Numerade Educator
01:50

Problem 36

The arch of a human foot acts like a spring during walking and jumping, storing energy as the foot stretches (i.e., the arch flattens) and returning energy as the foot recoils. In the data, $x$ is the vertical displacement of the arch, $f_{s}(x)$ is the force on the foot during stretching and $f_{r}(x)$ is the force during recoil (see Alexander's book Exploring Biomechanics): $$\begin{array}{|l|l|l|l|l|l|}
\hline x(\mathrm{mm}) & 0 & 2.0 & 4.0 & 6.0 & 8.0 \\\hline f_{s}(x)(\mathrm{N}) & 0 & 300 & 1000 & 1800 & 3500 \\\hline f_{r}(x)(\mathrm{N}) & 0 & 150 & 700 & 1300 & 3500 \\\hline\end{array}$$ Use Simpson's Rule to estimate the proportion of energy returned by the arch.

Caitlyn Axe
Caitlyn Axe
Numerade Educator
03:17

Problem 37

The velocities of two runners are given by $f(t)=10$ mph and $g(t)=10-\sin t$ mph. Find and interpret the integrals $\int_{0}^{\pi}[f(t)-g(t)] d t$ and $\int_{0}^{2 \pi}[f(t)-g(t)] d t$

Gregory Higby
Gregory Higby
Numerade Educator
05:03

Problem 38

The velocities of two racing cars $A$ and $B$ are given by $f(t)=40\left(1-e^{-t}\right)$ mph and $g(t)=20 t$ mph, respectively. The cars start at the same place at time $t=0 .$ Estimate
(a) the largest lead for car $A$ and (b) the time at which car $B$ catches up.

Vinnu M
Vinnu M
Numerade Educator
03:58

Problem 39

The graph shows the rate of flow of water in gallons per hour into and out of a tank. Assuming that the tank starts with 400 gallons, estimate the amount of water in the tank at hours 1,2,3,4 and 5 and sketch a graph of the amount of water in the tank.
GRAPH CANT COPY

Gregory Higby
Gregory Higby
Numerade Educator
02:46

Problem 40

The graph shows the rate of flow of water in gallons per hour into and out of a tank. Assuming that the tank starts with 400 gallons, estimate the amount of water in the tank at hours 1,2,3,4 and 5 and sketch a graph of the amount of water in the tank.
GRAPH CANT COPY

Gregory Higby
Gregory Higby
Numerade Educator
11:12

Problem 41

The graph shows the supply and demand curves for a product. The point of intersection $\left(q^{*}, p^{*}\right)$ gives the equilibrium quantity and equilibrium price for the product. The consumer surplus is defined to be $\mathrm{CS}=\int_{0}^{q^{*}} D(q) d q-p^{*} q^{*} .$ Shade in the area of the graph that represents the consumer surplus, and compute this in the case where $D(q)=10-\frac{1}{40} q$ and $S(t)=2+\frac{1}{120} q+\frac{1}{1200} q^{2}$
GRAPH CANT COPY

Oswaldo Jiménez
Oswaldo Jiménez
Numerade Educator
02:14

Problem 42

Repeat exercise 41 for the producer surplus defined by $\mathrm{PS}=p^{*} q^{*}-\int_{0}^{q *} S(q) d q$

Eric Mockensturm
Eric Mockensturm
Numerade Educator
01:18

Problem 43

Let $C^{\prime}(x)$ be the marginal cost of producing $x$ thousand copies of an item and let $R^{\prime}(x)$ be the marginal revenue from the sale of that item, with graphs as shown. Assume that $R^{\prime}(x)=C^{\prime}(x)$ at $x=2$ and $x=5 .$ Interpret the area between the curves for each interval: $(a) 0 \leq x \leq 2,$ (b) $2 \leq x \leq 5,$ (c) $0 \leq x \leq 5$ and
(d) $5 \leq x \leq 6$
GRAPH CANT COPY

Cinsy Krehbiel
Cinsy Krehbiel
Numerade Educator
01:07

Problem 44

A basic principle of economics is that profit is maximized when marginal cost equals marginal revenue. At which intersection is profit maximized in exercise $43 ?$ Explain your answer. In terms of profit, what does the other intersection point represent?

Dushyant Barot
Dushyant Barot
Numerade Educator
06:58

Problem 45

Suppose that the parabola $y=a x^{2}+b x+c$ and the line $y=m x+n$ intersect at $x=A$ and $x=B$ with $A<B .$ Show that the area between the curves equals $\frac{|a|}{6}(B-A)^{3} .$ (Hint: Use $A$ and $B$ to rewrite the integrand and then integrate.)

Harshita Goel
Harshita Goel
Numerade Educator
04:19

Problem 46

Suppose that the cubic $y=a x^{3}+b x^{2}+c x+d$ and the parabola $y=k x^{2}+m x+n$ intersect at $x=A$ and $x=B$ with B repeated (that is, the curves are tangent at $B$; see the figure). Show that the area between the curves equals $\frac{|a|}{12}(B-A)^{4}$
GRAPH CANT COPY

Paul Teng
Paul Teng
Numerade Educator

Problem 47

Consider two parabolas, each of which has its vertex at $x=0$ but with different concavities. Let $h$ be the difference in $y$ -coordinates of the vertices, and let $w$ be the difference in the $x$ -coordinates of the intersection points. Show that the area between the curves is $\frac{2}{3} h w$
GRAPH CANT COPY

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00:37

Problem 48

Show that for any constant $m$, the area between $y=2-x^{2}$ and $y=m x$ is $\frac{1}{6}\left(m^{2}+8\right)^{3 / 2} .$ Find the minimum such area.

Sriparna Bhattacharjee
Sriparna Bhattacharjee
Numerade Educator
01:10

Problem 49

For $y=x-x^{2}$ as shown, find the value of $L$ such that $A_{1}=A_{2}$
GRAPH CANT COPY

Brittany Scott
Brittany Scott
Numerade Educator
01:08

Problem 50

For $y=x-x^{2}$ and $y=k x$ as shown, find $k$ such that $A_{1}=A_{2}$
GRAPH CANT COPY

Carson Merrill
Carson Merrill
Numerade Educator