<h2 class="title">Applying Newton's Second Law of Motion</h2>
<p>Newton's second law can be applied to a variety of situations. We will look at the main types of examples that you need to study.</p>
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<h2>Example: Newton's Second Law: Box on a Surface</h2>
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<h3>Question</h3>
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<p>A $\text{10}$ $\text{kg}$ box is placed on a table. A horizontal force of magnitude $\text{32}$ $\text{N}$ is applied to the box. A frictional force of magnitude $\text{7}$ $\text{N}$ is present between the surface and the box.</p>
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<p>Draw a force diagram indicating all of the forces acting on the box.</p>
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<p>Calculate the acceleration of the box.</p>
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<img alt="032ec3f87cad2602d14c4d431e22fb52.png" src="https://data.ulearngo.com/assets/59dca26b-2b7b-4718-bd43-2fbfd046cf9b"/></div>
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<h3>Step 1: Identify the horizontal forces and draw a force diagram</h3>
<p>We only look at the forces acting in a horizontal direction (left-right) and not vertical (up-down) forces. The applied force and the force of friction will be included. The force of gravity, which is a vertical force, will not be included.</p>
<img alt="ca7a932573a3b0f5759b17933b813ac5.png" src="https://data.ulearngo.com/assets/c1929a73-b6f1-4a1a-b77b-2a03d85736ef"/></div>
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<h3>Step 2: Calculate the acceleration of the box</h3>
<p><strong>Remember</strong> that we consider the $y$- and $x$-directions separately. In this problem we can ignore the $y$-direction because the box is resting on a table with the gravitational force balanced by the normal force.</p>
<p>We have been given:</p>
<p>Applied force ${F}_{1}=\text{32}\text{ N}$</p>
<p>Frictional force ${F}_{f}=-\text{7}\text{ N}$</p>
<p>Mass $m=\text{10}\text{ kg}$</p>
<p>To calculate the acceleration of the box we will be using the equation $\vec{F}_{R}=m\vec{a}$.Therefore: \begin{align*}\vec{F}_R &amp;= m\vec{a} \\\vec{F}_1+\vec{F}_f &amp;= (\text{10})\vec{a} \\ (\text{32}-\text{7}) &amp;= (\text{10})\vec{a} \\\text{25} &amp;= (\text{10})\vec{a} \\\vec{a} &amp;= \text{2.5}\text{ m·s$^{-2}$}\ \text{to the left.}\end{align*}</p>
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Applying Newton's Second Law

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

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.


Applying Newton's Second Law

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