edits br

book/_config.yml

@@ -54,8 +54,8 @@ sphinx:
     html:
       use_multitoc_numbering: true
     #nb_render_text: ["remove-input", "hide-input"]  # to hide or remove input cells with tags
-
-
+
   extra_extensions:
     - sphinx_exercise
     #- extensions.fa_extension # for fontawesome icons needed when converting to pdf
+

book/demos/demo12/demo12.md

@@ -97,9 +97,9 @@ Increase attention and entertainment:
 The parallel between linear movements and rotations is interesting. The linear inertia is the mass $m$. The rotational inertia is called the moment of inertia in physics and is indicated by the letter $I$. For an object with a mass $m$ that turns around a fixed point at distance $r$ we have: $I=mr^2$
 
 Now compare the following situations:
-* *Linear movement*: $\Sigma F = ma \quad$ **(1)**<br>
+* *Linear movement*: $\Sigma F = ma \quad$ **(1)**\
 The sum of all forces on an object ($\Sigma F$) is equal to the product: mass ($m$) $\cdot$ acceleration ($a$).
-* *Rotational movement*:  $\Sigma \tau = I\alpha = mr^2\alpha \quad$ **(2)**<br>
+* *Rotational movement*:  $\Sigma \tau = I\alpha = mr^2\alpha \quad$ **(2)**\
 The sum of all torques ($\Sigma \tau$) that cause an angular acceleration ($\alpha$) is equal to the product of rotational inertia ($I$) $\cdot$ angular acceleration ($\alpha$).
 
 See a university level mechanics text for the restrictions to equations **(1)** and **(2)**.

book/demos/demo15/demo15.md

@@ -115,7 +115,7 @@ The phenomenon can be visualized by making graphs of the forces vs. time. You mi
 -	The rolling resistance force
 -	The resultant force
 
-Draw the graphs straight above one another with the same time axis.<br>
+Draw the graphs straight above one another with the same time axis.\
 Instead of sketching the graphs you could also have them calculated and drawn by means of a mathematics modelling programme.
 
 Of course, the motion of the cart and the pendulum can also be measured and analyzed, e.g. by means of a video-measurement. In the case of a symmetric pendulum the amplitudes of the cart and the pendulum could be compared to their masses.

book/demos/demo19/demo19.md

@@ -64,15 +64,14 @@ Schematic of the setup with the voltage source, ring and copper button. The bath
 2.  Now explain the set-up using the diagram on the board.
 3.  Then students return to their seats and answer the following questions on a worksheet:
 ```{exercise}
-{style=upper-alpha}
-**1.**  At three different points in the drawing indicate with arrows the direction of current, magnetic field, and Lorentz force.
-**2.**  Using the vectors drawn, explain the movement of the liquid.
-**3.**  Predict what we will observe when:
-  *a.* only the direction of the current is reversed,
-  *b.* only the direction of the magnetic field is reversed,
-  *c.* both are reversed.
-**4.**  Where would the candles experience the greatest force, near the center or near the edge of the circle? Why? How could you investigate this experimentally?
-**5.**  Does the Lorentz force have the same direction on moving Na$^+$ and Cl$^-$ ions? Explain.
+1. At three different points in the drawing indicate with arrows the direction of current, magnetic field, and Lorentz force.
+2. Using the vectors drawn, explain the movement of the liquid.
+3. Predict what we will observe when:
+    1. only the direction of the current is reversed,
+    2. only the direction of the magnetic field is reversed,
+    3. both are reversed.
+4. Where would the candles experience the greatest force, near the center or near the edge of the circle? Why? How could you investigate this experimentally?
+5. Does the Lorentz force have the same direction on moving Na$^+$ and Cl$^-$ ions? Explain.
 ```
 4.  Repeat the demonstration to check the answers to questions **C** and **D**.
 

book/demos/demo25/demo25.md

@@ -48,23 +48,24 @@ At the location (classroom or auditorium), think briefly about maximizing visibi
 ## Procedure
 The description is for a demo during an event with a large audience. For a demo in the classroom the teacher will include more interaction. 
 
-1. Take a (meter)stick, put it on the table, pull it slowly over the edge until it starts to tip over. Then put your finger under this tip-over-point and lift the stick. The stick remains balanced. <br>
+1. Take a (meter)stick, put it on the table, pull it slowly over the edge until it starts to tip over. Then put your finger under this tip-over-point and lift the stick. The stick remains balanced.
 - *It is as if all the mass of the stick is concentrated in that point. If we support that point, then the stick is balanced. That point we call the center of mass. As if that is where gravity acts on the stick.*
 2. We can shift the location of the center of mass by adding masses on the left or the right. If we put our purse or some other object on one side, then the center of mass shifts toward that side. Show this!
-3. The teacher stands on top of a chair or table for visibility, his/her side toward the audience.<br>
+3. The teacher stands on top of a chair or table for visibility, his/her side toward the audience.
 - *Our body also has a center of mass and that will probably be somewhere in our belly. Stand up everyone! Lean forward, farther and farther. What do you feel? Cramp in your toes? When we lean over so much that our center of mass passes over our toes, then we have to take a step forward to avoid falling.*
 - *Lift up your right leg forward. What happens to your shoulders? They go backward. Now lift up your right leg sideways. What happens to your shoulders? They move in the opposite direction to compensate, so that the center of mass remains above the left leg standing on the floor.*
-4. Everybody sits. The teacher remains sideways on top of the table and sinks through his/her legs. <br>
-- *My buttocks go backward, then something has to go forward to compensate. Knees and shoulders go forward.*<br><br> Alternative is to take someone from the audience to illustrate these movements.
-5. The teacher takes a backpack or other large bag and puts that under his sweater or jacket and walks like a 9-month pregnant woman. <br>
-- *There are times in life that the distribution of our mass changes. The shoulders have to go backward to compensate for the passenger up front, particularly when the pregnancy proceeds into the 9th month. Luckily after 9 months the passenger comes out and things go back to normal. However, men can have a similar problem with beer bellies and these do not go away after 9 months.* 
-<br><br>All of this takes some acting, but it is fun.
-6. Now hold the backpack in one hand with a stretched arm. <br>
+4. Everybody sits. The teacher remains sideways on top of the table and sinks through his/her legs.
+- *My buttocks go backward, then something has to go forward to compensate. Knees and shoulders go forward.*\
+Alternative is to take someone from the audience to illustrate these movements.
+5. The teacher takes a backpack or other large bag and puts that under his sweater or jacket and walks like a 9-month pregnant woman.
+- *There are times in life that the distribution of our mass changes. The shoulders have to go backward to compensate for the passenger up front, particularly when the pregnancy proceeds into the 9th month. Luckily after 9 months the passenger comes out and things go back to normal. However, men can have a similar problem with beer bellies and these do not go away after 9 months.*\
+All of this takes some acting, but it is fun.
+6. Now hold the backpack in one hand with a stretched arm.
 - *How does the body adjust to make sure that the center of mass of heavy backpack and body is still above the feet?*
 7. Take some people from the audience and put them with their heels and buttocks against the wall. Put a bank note of \$5 of \$10 or equivalent currency in front of their feet ({numref}`Figure {number} <demo25_fig3>`). 
-- *Keep your heels against the wall. If you can pick this up without falling, you can keep it.* 
-<br><br>But this is impossible, to pick up the banknote, the upper part of the body has to bend far, the center of mass will pass the toes. 
-8.  Show the photo of the child and the man on the see-saw. <br>
+- *Keep your heels against the wall. If you can pick this up without falling, you can keep it.*\
+But this is impossible, to pick up the banknote, the upper part of the body has to bend far, the center of mass will pass the toes. 
+8.  Show the photo of the child and the man on the see-saw.
 - *Is this possible? Is something wrong? Using the center of mass concept or the law of moments of force, how can you explain?*
 
 ```{figure} demo25_figure4.png

book/demos/demo27/demo27.md

@@ -17,7 +17,7 @@
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Concepts:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">heating and expansion of air, pressure, combustion</td>
     </tr>
-</table><br>
+</table>
 
 <div style="display: flex; justify-content: center;">
     <div style="position: relative; width: 70%; height: 0; padding-bottom: 56.25%;">
@@ -49,7 +49,7 @@ The teacher performs the experiment but is meant to mainly direct the discussion
 
 ```{figure} demo27_figure1.JPG
 ---
-width: 50%
+width: 70%
 align: center
 ---
 Place the glass or jar over the burning candle.
@@ -70,24 +70,24 @@ Let students brainstorm arguments for and against each explanation, exchange the
 
 ```{figure} demo27_figure2.JPG
 ---
-width: 50%
+width: 70%
 align: center
 ---
 The candle is extinguished. What made the liquid level rise?
 ```
 
 ## Physics background
-For explanation 3: With complete combustion of candle wax (mainly paraffin or stearin), roughly speaking, for every two molecules of O$_2$, one molecule of CO$_2$ and two molecules of H$_2$O are formed. When the flame extinguishes, the temperature drops sharply in that area, and H$_2$O precipitates there. The pressure in the glass quickly drops, the atmosphere pushes water inward until equilibrium is reached.
+**For explanation 3:** With complete combustion of candle wax (mainly paraffin or stearin), roughly speaking, for every two molecules of O$_2$, one molecule of CO$_2$ and two molecules of H$_2$O are formed. When the flame extinguishes, the temperature drops sharply in that area, and H$_2$O precipitates there. The pressure in the glass quickly drops, the atmosphere pushes water inward until equilibrium is reached.
 
-For explanation 2: Heat released to the surroundings of the glass also causes pressure reduction according to the general gas law. However, this process is slow, while the liquid level rises noticeably quickly.
+**For explanation 2:** Heat released to the surroundings of the glass also causes pressure reduction according to the general gas law. However, this process is slow, while the liquid level rises noticeably quickly.
 
-For explanation 1: For every oxygen molecule in the air, exactly one water molecule is formed. If that precipitates, the 'resulting space' can be filled by liquid. If we ignore the formation of CO$_2$, then even explanation 1 (according to quite a few biology textbooks the 'correct' one) is somewhat true.
+**For explanation 1:** For every oxygen molecule in the air, exactly one water molecule is formed. If that precipitates, the 'resulting space' can be filled by liquid. If we ignore the formation of CO$_2$, then even explanation 1 (according to quite a few biology textbooks the 'correct' one) is somewhat true.
 
 More important than the 'correct' explanation here is that students themselves come up with, defend, and evaluate arguments for and against the explanations. Another important aspect is that a need arises for empirical evidence.
 
 ```{figure} demo27_figure3.jpg
 ---
-width: 50%
+width: 70%
 align: center
 ---
 The balloon on the bottle inflates when you place the bottle in hot water.
@@ -114,22 +114,22 @@ Hold the can in the illustration of explanation 3 with tongs or oven mitts.
 
 **Scenario for a [POE Approach](../../Pedagogy/PoE.md)**
 
-**Predict**<br>
+**Predict**\
 Pour some (colored) water into the dish, place the candle in it, and light it. Get the glass ready. Explain that you are about to place the glass over the candle.
 
 Ask for a prediction of what will happen. Even very young children know that the candle will go out after a while. Older students may also know that the liquid will rise in the glass.
 
 (Ideally students' predictions are partially, but not entirely, accurate. This way, the observation result is not discouraging, but there is still room for learning.)
 
-**Observe**<br>
+**Observe**\
 Instruct the students to carefully observe what happens from the moment you place the glass over the candle, and to write down their observations as precisely as possible. Then place the glass and wait.
 
 Afterward, compare the observations. Everyone will have seen that the candle goes out, and some will have noticed air bubbles escaping at the beginning. Usually, not everyone notices that the flame gradually gets smaller rather than going out suddenly. Almost everyone sees the water rising in the glass, but it’s not always apparent that this only starts in earnest once the flame is out. Some note that the wick smokes for a while after the flame is out, and a few even observe condensation on the glass.
 
 It almost always turns out that not everyone sees exactly the same things. The teacher can point out that such differences are also very common among scientists and sometimes even necessary. This happens, for example, because they are interested in different aspects of the event: a biologist, chemist, or physicist might find different aspects of the extinguishing candle interesting.
 
-**Explain**<br>
-*The water replaces the oxygen consumed by combustion.*<br>
+**Explain**\
+*The water replaces the oxygen consumed by combustion.*\
 Students learn that oxygen is necessary for combustion. When the oxygen is depleted, the candle goes out. Some biology textbooks explain the rising liquid level in this experiment by saying that the water rises to replace the disappeared oxygen. The water often does indeed fill a part of the glass that roughly corresponds to the percentage of oxygen in the atmosphere according to Binas (a Dutch reference book): 21%.
 
 But this is strange: according to chemistry, the oxygen atoms are all still there, just in different compounds than at the beginning. If there are still exactly the same number of atoms, how can there be room for the water to fill? What do the students think, is this explanation correct after all or can they think of an alternative?
@@ -143,7 +143,7 @@ Have students choose the explanation they think is best and come up with argumen
 
 In conclusion, the teacher may explain that it is not unusual for scientists to disagree. They can also find different observations important and accept different explanations. The smartest and most creative scientists find the best observations and arguments in favour of some claims (often their own) and against others (usually those of competitors). This has proven to be an excellent approach for the rapid development of reliable scientific knowledge.
 
-**Further options**<br>
+**Further options**\
 To practice observing carefully, set up a webcam for the experiment and replay the events. Have students record their qualitative observations again and note the times. Build a description of events and times on the board. Subsequently, the discussion of explanations can always be linked to direct references to the observations. This raises the scientific level of the activities somewhat.
 
 Instead of presenting students with possible explanations, you can also have them come up with explanations themselves and a practical way to test them. This will take (much) more time.

book/demos/demo34/demo34.md

@@ -17,7 +17,7 @@
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Concepts:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">density, floating, sinking, suspension</td>
     </tr>
-</table><br>
+</table>
 
 ```{figure} demo34_figure4.png
 ---

book/demos/demo40/demo40.md

@@ -17,7 +17,7 @@
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Concepts:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Torque, spring energy, kinetic energy, equilibrium</td>
     </tr>
-</table><br>
+</table>
 
 <div style="display: flex; justify-content: center;">
     <div style="position: relative; width: 70%; height: 0; padding-bottom: 56.25%;">

book/demos/demo51/demo51.md

@@ -23,7 +23,7 @@ align: right
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Concepts:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Thermal radiation, reflection and absorption, parabolic mirror, focal point</td>
     </tr>
-</table><br>
+</table>
 
 ## Introduction
 Heat is – in popular terms – a form of energy. Its counterpart is ‘cold’. You can get rid of cold by adding heat. You can't get rid of heat by adding cold, although it might seem that way when you open a window in winter. In fact, heat escapes. Heat is 'something', cold is 'nothing'. 

book/demos/demo58/demo58.md

@@ -22,7 +22,7 @@ align: right
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Concepts:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Angular velocity, orbital velocity, centripetal force</td>
     </tr>
-</table><br>
+</table>
 
 ## Introduction
 Students often find concepts linked to circular motion difficult. Examples include the difference between orbital velocity and angular velocity and understanding the centripetal force. In this demonstration, you combine these concepts with the frictional force to create a situation where only one force provides the centripetal force. 

book/demos/demo60/demo60.md

@@ -19,7 +19,7 @@ align: right
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Age group:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">from grade 8, extension availabe for grade 11 and above</td>
     </tr>
-</table><br>
+</table>
 
 <div style="display: flex; justify-content: center;">
     <div style="position: relative; width: 70%; height: 0; padding-bottom: 56.25%;">

book/demos/demo61/demo61.md

@@ -13,7 +13,7 @@
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Age group:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">12-14</td>
     </tr>
-</table><br>
+</table>
 
 ## Introduction
 Everyone is familiar with the demonstration of a burning candle that goes out when placed under a bell jar. A slightly altered version of that demonstration provides excellent opportunity to highlight some characteristics of how science works. For this demonstration you make use of two burning candles of different lengths, placed under the bell jar. 

book/demos/demo62/demo62.ipynb

@@ -25,7 +25,7 @@
     "        <td style=\"text-align: left; padding: 3px; border: none; color: var(--text-color)\">Age group:</td>\n",
     "        <td style=\"text-align: left; padding: 3px; border: none; color: var(--text-color)\">15-18</td>\n",
     "    </tr>\n",
-    "</table><br>\n",
+    "</table>\n",
     "\n",
     "## Introduction\n",
     "Modern smartphones have a LiDAR sensor. This sensor allows you to measure the distance to objects. The LiDAR sensor is designed to measure only in air. As the speed of light in a transparent substance is slightly different than the speed of light in air, the measured distance is different. You can use this 'measurement error' to determine the speed of light in a transparent liquid.\n",

book/demos/demo64/demo64.md

@@ -23,7 +23,7 @@ align: right
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Concepts:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Boiling </td>
     </tr>
-</table><br>
+</table>
 
 
 ## Introduction

book/demos/demo65/demo65.md

@@ -20,7 +20,7 @@ align: right
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Age group:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">14-18</td>
     </tr>
-</table><br>
+</table>
 
 
 ## Introduction