Chapter 14: Problem 31
Evaluate the indefinite integral. $$\int(3 \mathbf{i}+4 t \mathbf{j}) d t$$
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Chapter 14: Problem 31
Evaluate the indefinite integral. $$\int(3 \mathbf{i}+4 t \mathbf{j}) d t$$
These are the key concepts you need to understand to accurately answer the question.
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At time \(t=0\) a baseball that is \(5 \mathrm{ft}\) above the ground is hit with a bat. The ball leaves the bat with a speed of \(80 \mathrm{ft} / \mathrm{s}\) at an angle of \(30^{\circ}\) above the horizontal. (a) How long will it take for the baseball to hit the ground? Express your answer to the nearest hundredth of a second. (b) Use the result in part (a) to find the horizontal distance traveled by the ball. Express your answer to the nearest tenth of a foot.
We assume that \(s\) is an arc length parameter for a smooth vector-valued function \(\mathbf{r}(s)\) in 3 -space and that \(d\) T/ds and \(d\) N/ds exist at each point on the curve. This implies that \(d\) B/ds exists as well, since \(\mathbf{B}=\mathbf{T} \times \mathbf{N} .\) (a) Show that \(d \mathbf{B} / d s\) is perpendicular to \(\mathbf{B}(s)\) (b) Show that \(d \mathbf{B} / d s\) is perpendicular to \(\mathbf{T}(s) .\) [Hint: Use the fact that \(\mathbf{B}(s)\) is perpendicular to both \(\mathbf{T}(s)\) and \(\mathbf{N}(s)\) and differentiate \(\mathbf{B} \cdot \mathbf{T}\) with respect to \(s .1\) (c) Use the results in parts (a) and (b) to show that \(d\) B /ds is a scalar multiple of \(\mathbf{N}(s) .\) The negative of this scalar is called the torsion of \(\mathbf{r}(s)\) and is denoted by \(\tau(s) .\) Thus, $$\frac{d \mathbf{B}}{d s}=-\tau(s) \mathbf{N}(s)$$ (d) Show that \(\tau(s)=0\) for all \(s\) if the graph of \(\mathbf{r}(s)\) lies in a plane. INote: For reasons that we cannot discuss here, the torsion is related to the "twisting" properties of the curve, and \(\tau(s)\) is regarded as a numerical measure of the tendency for the curve to twist out of the osculating plane. \(]\)
Find parametric equations of the line tangent to the graph of \(\mathbf{r}(t)\) at the point where \(t=t_{0}\) $$\mathbf{r}(t)=e^{2 t} \mathbf{i}-2 \cos 3 t \mathbf{j}: t_{0}=0$$
Solve the vector initial-value problem for \(y(t)\) by integrating and using the initial conditions to find the constants of integration. $$y^{\prime}(t)=t^{2} \mathbf{i}+2 t \mathbf{j}, \quad \mathbf{y}(0)=\mathbf{i}+\mathbf{j}$$
The position vectors of two particles are given. Show that the particles move along the same path but the speed of the first is constant and the speed of the second is not. $$\begin{array}{ll} \mathbf{r}_{1}=2 \cos 3 t \mathbf{i}+2 \sin 3 t \mathbf{j} \\ \mathbf{r}_{2}=2 \cos \left(t^{2}\right) \mathbf{i}+2 \sin \left(t^{2}\right) \mathbf{j} & (t \geq 0) \end{array}$$
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