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      <text>9.4.1.1 The right-handed screw rule</text>
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      <text><![CDATA[<h4><b>The right-handed screw rule</b></h4><p>To understand how the vector product is formed it is helpful to consider first the right-handed screw rule. Consider the two vectors <span class="math inline">\(\underline{a}\)</span> and <span class="math inline">\(\underline{b}\)</span> shown in the following figure.</p>
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<img src="@@PLUGINFILE@@/block5fig1.svg" alt="vectors a and b with coinciding tails and the angle theta between them" width="304" height="116" role="presentation" class="img-responsive atto_image_button_text-bottom">
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<p>The two vectors lie in a plane; this plane is shaded in the figure above. The following figure shows the same two vectors and the plane in which they lie together with a unit vector denoted <span class="math inline">\(\hat{\underline{e}}\)</span>, which is perpendicular to this plane. Imagine turning a right-handed screw, aligned along <span class="math inline">\(\underline{\hat{e}}\)</span>, in the direction from <span class="math inline">\(\underline{a}\)</span> towards <span class="math inline">\(\underline{b}\)</span> as shown. A right-handed screw is one which when turned clockwise enters the material into which it is being screwed (most screws are of this kind). You will see from the figure below that the screw will advance in the direction of <span class="math inline">\(\hat{\underline{e}}\)</span>.<br></p>
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<img src="@@PLUGINFILE@@/block5fig2.svg" alt="clockwise turning of the screw sitting along e" width="227" height="161" role="presentation" class="img-responsive atto_image_button_text-bottom">
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<p style="text-align: left;">On the other hand, if the right-handed screw is turned from <span class="math inline">\(\underline{b}\)</span> towards <span class="math inline">\(\underline{a}\)</span> the screw will retract in the direction of <span class="math inline">\(\underline{\hat{f}}\)</span> as shown in the following figure.<br></p>
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<img src="@@PLUGINFILE@@/block5fig3.svg" alt="anticlockwise turning of the screw sitting along e" width="233" height="122" role="presentation" class="img-responsive atto_image_button_text-bottom">
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<p style="text-align: left;">We are now in a position to describe the vector product.<br></p>]]></text>
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<file name="block5fig3.svg" path="/" encoding="base64">[encoded data, 31276 characters]</file>
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