<p>The following examples deal with finding static friction.</p>
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<h2>Example:</h2>
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<h3>Question</h3>
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<p>A box resting on a surface experiences a normal force of magnitude \(\text{30}\) \(\text{N}\) and the coefficient of static friction tween the surface and the box, \(\mu_s\), is \(\text{0.34}\). What is the maximum static frictional force?</p>
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<h3>Step 1: Maximum static friction</h3>
<p>We know that the relationship between the maximum static friction, \(f_s^{max}\), the coefficient of static friction, \(\mu_s\) and the normal, \(N\), to be:\[f_s^{max} = \mu_sN\]</p>
<p>We have been given that \(\mu_s = \text{0.34}\) and \(N=\text{30}\text{ N}\). This is all of the information required to do the calculation.</p>
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<h3>Step 2: Calculate the result</h3>
<p>\begin{align*} f_s^{max} &amp;= \mu_sN \\ &amp;= (\text{0,34})(\text{30}) \\ &amp; = \text{10,2} \end{align*}</p>
<p>The maximum magnitude of static friction is \(\text{10.2}\) \(\text{N}\).</p>
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<h2>Example:</h2>
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<h3>Question</h3>
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<p>The forwards of your school's rugby team are trying to push their scrum machine. The normal force exerted on the scrum machine is \(\text{10 000}\) \(\text{N}\). The machine isn't moving at all. If the coefficient of static friction is \(\text{0.78}\) what is the minimum force they need to exert to get the scrum machine to start moving?</p>
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<h3>Step 1: Minimum or maximum</h3>
<p>The question asks what the minimum force required to get the scrum machine moving will be. We don't know a relationship for this but we do know how to calculate the maximum force of static friction. The forwards need to exert a force greater than this so the minimum amount they can exert is in fact equal to the maximum force of static friction.</p>
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<h3>Step 2: Maximum static friction</h3>
<p>We know that the relationship between the maximum static friction, \(f_s^{max}\), the coefficient of static friction, \(\mu_s\) and the normal, \(N\), to be:\[f_s^{max} = \mu_sN\]</p>
<p>We have been given that \(\mu_s = \text{0.78}\) and \(N=\text{10 000}\text{ N}\). This is all of the information required to do the calculation.</p>
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<h3>Step 3: Calculate the result</h3>
<p>\begin{align*} f_s^{max} &amp;= \mu_sN \\ &amp;= (\text{0,78})(\text{10 000}) \\ &amp; = \text{7 800}\text{ N} \end{align*}</p>
<p>The maximum magnitude of static friction is \(\text{7 800}\) \(\text{N}\).</p>
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Finding Static Friction

Physics is a science discipline concerned with the nature and properties of matter and energy. Physics topics include mechanics, heat, light and radiation, sound, electricity, magnetism, the structure of atoms, and so on.

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Learn about the principles of motion and forces, including static and kinetic friction, normal forces, tension, and Newton&#8217;s laws, with practical examples such as lifting weights, rockets, and balloons.


Finding Static Friction

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