Chapter 7: Problem 2
Does a computer algebra system give an exact result for an indefinite integral? Explain.
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Chapter 7: Problem 2
Does a computer algebra system give an exact result for an indefinite integral? Explain.
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Use the indicated methods to solve the following problems with nonuniform grids. A hot-air balloon is launched from an elevation of 5400 ft above sea level. As it rises, its vertical velocity is computed using a device (called a variometer) that measures the change in atmospheric pressure. The vertical velocities at selected times are shown in the table (with units of \(\mathrm{ft} / \mathrm{min}\) ). $$\begin{array}{|l|c|c|c|c|c|c|c|} \hline t \text { (min) } & 0 & 1 & 1.5 & 3 & 3.5 & 4 & 5 \\ \hline \begin{array}{l} \text { Velocity } \\ \text { (ft/min) } \end{array} & 0 & 100 & 120 & 150 & 110 & 90 & 80 \\ \hline \end{array}$$ a. Use the Trapezoid Rule to estimate the elevation of the balloon after five minutes. Remember that the balloon starts at an elevation of \(5400 \mathrm{ft}\) b. Use a right Riemann sum to estimate the elevation of the balloon after five minutes. c. A polynomial that fits the data reasonably well is $$g(t)=3.49 t^{3}-43.21 t^{2}+142.43 t-1.75$$ Estimate the elevation of the balloon after five minutes using this polynomial.
\(A n\) integrand with trigonometric functions in the numerator and denominator can often be converted to a rational integrand using the substitution \(u=\tan (x / 2)\) or equivalently \(x=2 \tan ^{-1} u .\) The following relations are used in making this change of variables. \(A: d x=\frac{2}{1+u^{2}} d u \quad B: \sin x=\frac{2 u}{1+u^{2}} \quad C: \cos x=\frac{1-u^{2}}{1+u^{2}}\) $$\text { Evaluate } \int_{0}^{\pi / 2} \frac{d \theta}{\cos \theta+\sin \theta}$$
Determine whether the following statements are true and give an explanation or counterexample. a. The general solution of \(y^{\prime}(t)=20 y\) is \(y=e^{20 t}\). b. The functions \(y=2 e^{-2 t}\) and \(y=10 e^{-2 t}\) do not both satisfy the differential equation \(y^{\prime}+2 y=0\). c. The equation \(y^{\prime}(t)=t y+2 y+2 t+4\) is not separable. d. A solution of \(y^{\prime}(t)=2 \sqrt{y}\) is \(y=(t+1)^{2}\).
Approximate the following integrals using Simpson's Rule. Experiment with values of \(n\) to ensure that the error is less than \(10^{-3}\). \(\int_{0}^{\pi} \frac{4 \cos x}{5-4 \cos x} d x=\frac{2 \pi}{3}\)
An object in free fall may be modeled by assuming that the only forces at work
are the gravitational force and resistance (friction due to the medium in
which the object falls). By Newton's second law (mass \(\times\) acceleration
\(=\) the sum of the external forces), the velocity of the object satisfies the
differential equation $$m \quad \cdot \quad v^{\prime}(t)=m g+f(v)$$, where
\(f\) is a function that models the resistance and the positive direction is
downward. One common assumption (often used for motion in air) is that
\(f(v)=-k v^{2},\) where \(k>0\) is a drag coefficient.
a. Show that the equation can be written in the form \(v^{\prime}(t)=\) \(g-a
v^{2},\) where \(a=k / m\).
b. For what (positive) value of \(v\) is \(v^{\prime}(t)=0 ?\) (This equilibrium
solution is called the terminal velocity.)
c. Find the solution of this separable equation assuming \(v(0)=0\) and
\(0
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