mirror of
https://github.com/HananoshikaYomaru/openfreebooks.git
synced 2026-11-13 04:55:51 +00:00
55 lines
1.8 KiB
HTML
55 lines
1.8 KiB
HTML
<div class="book-prose">
|
|
<h2 id="examples" class="book-prose__heading">Worked checkpoints</h2>
|
|
<p>
|
|
These quick prompts are designed for class discussion or self-check before moving to momentum
|
|
and energy.
|
|
</p>
|
|
|
|
<details class="book-question">
|
|
<summary class="book-question__prompt">
|
|
A 4 kg trolley is pulled right with 18 N while friction is 10 N left. What is its acceleration?
|
|
</summary>
|
|
<div class="book-question__solution">
|
|
<p>
|
|
Net force \(= 18 - 10 = 8\text{ N}\) to the right, so
|
|
\(a = F_{\text{net}}/m = 8/4 = 2\text{ m s}^{-2}\) to the right.
|
|
</p>
|
|
</div>
|
|
</details>
|
|
|
|
<details class="book-question">
|
|
<summary class="book-question__prompt">
|
|
Why can a book stay at rest on a table even though gravity is acting?
|
|
</summary>
|
|
<div class="book-question__solution">
|
|
<p>
|
|
Gravity pulls down, but the table exerts an equal normal force upward. Net force is zero, so
|
|
acceleration is zero.
|
|
</p>
|
|
</div>
|
|
</details>
|
|
|
|
<details class="book-question">
|
|
<summary class="book-question__prompt">
|
|
A rocket pushes exhaust gas backward. Which Newton's law explains forward thrust?
|
|
</summary>
|
|
<div class="book-question__solution">
|
|
<p>
|
|
Newton's third law. The rocket pushes gas backward; the gas pushes the rocket forward with an
|
|
equal and opposite force.
|
|
</p>
|
|
</div>
|
|
</details>
|
|
|
|
<details class="book-question">
|
|
<summary class="book-question__prompt">
|
|
In the motion lab, what happens to the velocity-time line when acceleration is set to zero?
|
|
</summary>
|
|
<div class="book-question__solution">
|
|
<p>
|
|
The line becomes horizontal, showing constant velocity. Position then changes linearly with
|
|
time.
|
|
</p>
|
|
</div>
|
|
</details>
|
|
</div>
|