<h2>Summary</h2>
<ul>
<li>Friction is a contact force between systems that opposes the motion or attempted motion between them. Simple friction is proportional to the normal force \(N\) pushing the systems together. (A normal force is always perpendicular to the contact surface between systems.) Friction depends on both of the materials involved. The magnitude of static friction\({f}_{\text{s}}\) between systems stationary relative to one another is given by

<div>\({f}_{\text{s}}\le {\mu }_{\text{s}}N,\)</div>

where \({\mu }_{\text{s}}\) is the coefficient of static friction, which depends on both of the materials.</li>
<li>The kinetic friction force \({f}_{\text{k}}\) between systems moving relative to one another is given by

<div>\({f}_{\text{k}}={\mu }_{\text{k}}N,\)</div>

where \({\mu }_{\text{k}}\) is the coefficient of kinetic friction, which also depends on both materials.</li>
</ul>
<h2>Glossary</h2>
<h3>friction</h3>
<p>a force that opposes relative motion or attempts at motion between systems in contact</p>
<h3>kinetic friction</h3>
<p>a force that opposes the motion of two systems that are in contact and moving relative to one another</p>
<h3>static friction</h3>
<p>a force that opposes the motion of two systems that are in contact and are not moving relative to one another</p>
<h3>magnitude of static friction</h3>
<p>\({f}_{s}\le {\mu }_{s}\phantom{\rule{0.25em}{0ex}}N\), where \({\mu }_{s}\) is the coefficient of static friction and \(N\) is the magnitude of the normal force</p>
<h3>magnitude of kinetic friction</h3>
<p>\({f}_{k}={\mu }_{k}N\), where \({\mu }_{k}\) is the coefficient of kinetic friction</p>
<section data-element-type="conceptual-questions"></section>

1c4ddb66-ad36-4f81-90e7-4629f497d0b4

Summarizing 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.

Physics

Explore the scientific principles of friction, drag, and elasticity, including topics such as Newton&#8217;s Laws, stress and strain, compression, tension, and bulk and shear modulus.


Summarizing Friction

Track Your Learning Progress