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55 lines
1.8 KiB
HTML
55 lines
1.8 KiB
HTML
<div class="book-prose">
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<h2 id="examples" class="book-prose__heading">Worked checkpoints</h2>
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<p>
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These quick prompts are designed for class discussion or self-check before moving to momentum
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and energy.
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</p>
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<details class="book-question">
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<summary class="book-question__prompt">
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A 4 kg trolley is pulled right with 18 N while friction is 10 N left. What is its acceleration?
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</summary>
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<div class="book-question__solution">
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<p>
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Net force \(= 18 - 10 = 8\text{ N}\) to the right, so
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\(a = F_{\text{net}}/m = 8/4 = 2\text{ m s}^{-2}\) to the right.
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</p>
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</div>
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</details>
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<details class="book-question">
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<summary class="book-question__prompt">
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Why can a book stay at rest on a table even though gravity is acting?
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</summary>
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<div class="book-question__solution">
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<p>
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Gravity pulls down, but the table exerts an equal normal force upward. Net force is zero, so
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acceleration is zero.
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</p>
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</div>
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</details>
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<details class="book-question">
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<summary class="book-question__prompt">
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A rocket pushes exhaust gas backward. Which Newton's law explains forward thrust?
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</summary>
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<div class="book-question__solution">
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<p>
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Newton's third law. The rocket pushes gas backward; the gas pushes the rocket forward with an
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equal and opposite force.
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</p>
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</div>
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</details>
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<details class="book-question">
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<summary class="book-question__prompt">
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In the motion lab, what happens to the velocity-time line when acceleration is set to zero?
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</summary>
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<div class="book-question__solution">
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<p>
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The line becomes horizontal, showing constant velocity. Position then changes linearly with
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time.
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</p>
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</div>
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</details>
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</div>
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