Suppose that the matrix \(H\) in \((1.5)\) is given by $$ H=\frac{1}{\sqrt{6}}\left(\begin{array}{ccc} \sqrt{2} & \sqrt{2} & \sqrt{2} \\ -2 & 1 & 1 \\ 0 & -\sqrt{3} & \sqrt{3} \end{array}\right) $$ Check that \(H^{\mathrm{t}} H=H H^{\mathrm{t}}=I\). Write down the components of \(\boldsymbol{e}_{1}\), \(e_{2}\), and \(e_{3}\) in \(\tilde{T}\), and the components of \(\tilde{e}_{1}, \tilde{e}_{2}\), and \(\tilde{e}_{3}\) in \(\mathcal{T}\).

Short Answer

Expert verified
The transpose of the matrix \(H\) is: $$ H^{\mathrm{t}}= \frac{1}{\sqrt{6}}\left(\begin{array}{ccc} \sqrt{2} & -2 & 0 \\\ \sqrt{2} & 1 & -\sqrt{3} \\\ \sqrt{2} & 1 & \sqrt{3} \end{array}\right) $$ 2. What are the components of \(e_1, e_2, e_3\) in \(\tilde{T}\)? The components of \(e_1, e_2, e_3\) in \(\tilde{T}\) are: $$ \boldsymbol{e_1}_{\tilde{T}}= \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ -2 \\ 0 \end{array}\right), \quad \boldsymbol{e_2}_{\tilde{T}} = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ 1 \\ -\sqrt{3} \end{array}\right), \quad \boldsymbol{e_3}_{\tilde{T}} = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ 1 \\ \sqrt{3} \end{array}\right) $$ 3. What are the components of \(\tilde{e}_1, \tilde{e}_2, \tilde{e}_3\) in \(\mathcal{T}\)? The components of \(\tilde{e}_1, \tilde{e}_2, \tilde{e}_3\) in \(\mathcal{T}\) are: $$ \boldsymbol{\tilde{e}_1}_{\mathcal{T}}= \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ -2 \\ 0 \end{array}\right), \quad \boldsymbol{\tilde{e}_2}_{\mathcal{T}} = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ 1 \\ -\sqrt{3} \end{array}\right), \quad \boldsymbol{\tilde{e}_3}_{\mathcal{T}} = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ 1 \\ \sqrt{3} \end{array}\right) $$

Step by step solution

01

Find the transpose of matrix H

Calculate the transpose of the matrix \(H\) by interchanging its rows with columns: $$ H^{\mathrm{t}}= \frac{1}{\sqrt{6}}\left(\begin{array}{ccc} \sqrt{2} & -2 & 0 \\\ \sqrt{2} & 1 & -\sqrt{3} \\\ \sqrt{2} & 1 & \sqrt{3} \end{array}\right) $$
02

Perform matrix multiplication

Multiply the matrices \(H^{\mathrm{t}}\) and \(H\), and then \(H\) and \(H^{\mathrm{t}}\): $$ H^{\mathrm{t}}H = \frac{1}{6}\left(\begin{array}{ccc} 6 & 0 & 0 \\\ 0 & 6 & 0 \\\ 0 & 0 & 6 \end{array}\right) = I $$ $$ HH^{\mathrm{t}} = \frac{1}{6}\left(\begin{array}{ccc} 6 & 0 & 0 \\\ 0 & 6 & 0 \\\ 0 & 0 & 6 \end{array}\right) = I $$
03

Find components of \(e_1, e_2, e_3\) in \(\tilde{T}\)

Multiply the matrix \(H\) with each of the basis vectors \(e_1, e_2, e_3\) of \(\mathcal{T}\) to find their components in \(\tilde{T}\): $$ e_1 = \left(\begin{array}{c} 1 \\ 0 \\ 0 \end{array}\right) $$ $$ \boldsymbol{e_1}_{\tilde{T}}=He_1 = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ -2 \\ 0 \end{array}\right) $$ Similarly, for \(e_2\) and \(e_3\): $$ \boldsymbol{e_2}_{\tilde{T}} = He_2 = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ 1 \\ -\sqrt{3} \end{array}\right) $$ $$ \boldsymbol{e_3}_{\tilde{T}} = He_3 = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ 1 \\ \sqrt{3} \end{array}\right) $$
04

Find the components of \(\tilde{e}_1, \tilde{e}_2, \tilde{e}_3\) in \(\mathcal{T}\)

Multiply the transpose of matrix \(H\) with each of the basis vectors \(\tilde{e}_1, \tilde{e}_2, \tilde{e}_3\) of \(\tilde{T}\) to find their components in \(\mathcal{T}\): $$ \tilde{e}_1 = \left(\begin{array}{c} 1 \\ 0 \\ 0 \end{array}\right) $$ $$ \boldsymbol{\tilde{e}_1}_{\mathcal{T}}=H^{\mathrm t}\tilde{e}_1 = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ -2 \\ 0 \end{array}\right) $$ Similarly, for \(\tilde{e}_2\) and \(\tilde{e}_3\): $$ \boldsymbol{\tilde{e}_2}_{\mathcal{T}} = H^{\mathrm t}\tilde{e}_2 = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ 1 \\ -\sqrt{3} \end{array}\right) $$ $$ \boldsymbol{\tilde{e}_3}_{\mathcal{T}} = H^{\mathrm t}\tilde{e}_3 = \frac{1}{\sqrt{6}}\left(\begin{array}{c} \sqrt{2} \\ 1 \\ \sqrt{3} \end{array}\right) $$

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Most popular questions from this chapter

What are the transition matrices for rotations through \(\pm 2 \pi / 3\) about an axis aligned with the vector with \(\mathcal{T}\)-components \((1,1,1) ?\)

\({ }^{\dagger} \mathrm{A}\) small bead is threaded on a smooth wire in the shape of a curve given parametrically by \(\boldsymbol{r}=\boldsymbol{r}(q)\). The wire rotates with constant angular velocity about a vertical axis. Show that $$ \frac{\mathrm{d}}{\mathrm{d} t}\left[\frac{1}{2} \dot{q}^{2} \frac{\mathrm{d} \boldsymbol{r}}{\mathrm{d} q} \cdot \frac{\mathrm{d} \boldsymbol{r}}{\mathrm{d} q}\right]=\dot{q} \frac{\mathrm{d} \boldsymbol{r}}{\mathrm{d} q} \cdot \ddot{\boldsymbol{r}} $$ where the dot is the time derivative relative to a frame rotating with the wire, and \(\boldsymbol{r}\) is measured from an origin on the axis Deduce that $$ \frac{\mathrm{d} \boldsymbol{r}}{\mathrm{d} q} \cdot \frac{\mathrm{d} \boldsymbol{r}}{\mathrm{d} q} \dot{q}^{2}-(\boldsymbol{\omega} \wedge \boldsymbol{r}) \cdot(\boldsymbol{\omega} \wedge \boldsymbol{r})-2 \boldsymbol{g} \cdot \boldsymbol{r}=\text { constant. } $$ Does this result still hold when the axis of rotation is not vertical?

Show that if \(\tilde{e}_{i}=\sum_{j} H_{j i} e_{j}\) where \(\left(e_{1}, e_{2}, e_{3}\right)\) is an orthonormal triad, then $$ \tilde{e}_{1} \cdot\left(\tilde{e}_{2} \wedge \tilde{e}_{3}\right)=\operatorname{det}(H) e_{1} \cdot\left(e_{2} \wedge e_{3}\right) . $$ Deduce that if \(\tilde{\mathcal{T}}=\left(\tilde{e}_{1}, \tilde{e}_{2}, \tilde{e}_{3}\right)\) and \(\mathcal{T}=\left(e_{1}, e_{2}, e_{3}\right)\) are right-handed orthonormal triads, then the transition matrix from \(\tilde{T}\) to \(\mathcal{T}\) is a proper orthogonal matrix.

A sphere of radius \(a\) is rolling without slipping on a rough horizontal plane in such a way that its centre traces out a horizontal circle, radius \(b\) and centre \(O\), with constant angular speed \(\Omega\). Let \((i, j, k)\) be an orthonormal triad with \(k\) vertical and \(i\) in the direction from \(O\) to the centre of the sphere. Show that the angular velocity of the sphere relative to the plane satisfies $$ \boldsymbol{\omega}=n \boldsymbol{k}-\frac{b}{a} \Omega i $$ where \(n=\boldsymbol{\omega} \cdot \boldsymbol{k}\). Show that if \(n\) is constant, then the locus of the point of contact on the sphere is a circle. What is its radius?

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