update 18, 29, 43

book/demos/demo18/demo18.md

@@ -93,7 +93,7 @@ A can with a hole.
     </div>
 </div>
 
-*A variation of the demonstration described above.* 
+*A variation on the demonstration described above.* 
 
 
 ```{tip}

book/demos/demo29/demo29.md

@@ -51,7 +51,7 @@ Diagram of a burning tea light candle and a glass with vinegar and baking soda.
 * Baking soda or soda
 
 ## Preparation
-Put vinegar and baking soda or soda in the jar. Not too much, as it will bubble and overflow from the jar. The bubbling is caused by the carbon dioxide gas that is released.
+Put vinegar and baking soda or soda in the jar. Not too much, as it will bubble and overflow from the jar. This can be clearly seen in the video. The bubbling is caused by the carbon dioxide gas that is released.
 
 ## Procedure
 1. Place the candle in a glass and light it.
@@ -79,7 +79,7 @@ The tea light candle is extinguished by something invisible... what is it?
 Baking soda and vinegar react with each other, producing carbon dioxide. This gas is heavier than air and remains in the glass, and it's invisible. Pouring it over the candle, this gas extinguishes the candle flame without seeming to have done anything.
 
 ```{tip}
-* After the demonstration, you can talk about the dangers of suffocation due to CO2 and other heavy gases. An example is the Nyos disaster in 1986, where a large number of residents in Cameroon were suffocated in their sleep due to the sudden release of CO$_2$ from a volcanic crater lake.
+* After the demonstration, you can talk about the dangers of suffocation due to CO2 and other heavy gases. An example is the [Nyos disaster](https://en.wikipedia.org/wiki/Lake_Nyos_disaster) in 1986, where a large number of residents in Cameroon were suffocated in their sleep due to the sudden release of CO$_2$ from a volcanic crater lake.
 * Show a fire extinguisher that relies on this extinguishing effect of carbon dioxide. These extinguishers are easily recognizable because they have a black expansion tube or snow tube at the end of the hose. There is a handle between the expansion tube and the hose that must be held during use of the extinguisher. The handle is necessary because the end of the unprotected tube becomes very cold (up to about -80°C), and one can suffer third-degree burns from this extreme cold.
 ```
 

book/demos/demo43/demo43.md

@@ -3,7 +3,7 @@
 <table style="width: 100%; border-collapse: collapse; border: none;">
     <tr style="background-color: var(--background-color);">  
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Authors:</td>
-        <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Ed van den Berg, Loran de Vries, Onne Slooten</td>
+        <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Ed van den Berg, Loran de Vries & Onne Slooten</td>
     </tr>
     <tr style="background-color: var(--background-color);"> 
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Time:</td>
@@ -19,9 +19,32 @@
     </tr>
 </table>
 
+<div style="display: flex; justify-content: center;">
+    <div style="position: relative; width: 70%; height: 0; padding-bottom: 56.25%;">
+        <iframe
+            src="https://www.youtube.com/embed/ZH0U1InSbMQ?si=tg14Hp8TYEE07BD_"
+            style="position: absolute; top: 0; left: 0; width: 100%; height: 100%;"
+            frameborder="0"
+            allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"
+            allowfullscreen
+        ></iframe>
+    </div>
+</div>
+
 ## Introduction
 How can you experience force and motion in person without too much interference from that annoying, always present friction? With a bowling ball! During this demonstration in the hallway or gymnasium, some students try to influence the direction of a bowling ball with brooms and feel the essence of Newton's first and second law.
 
+<!--
+```{figure} demo43_fig1.jpg
+---
+width: 50%
+align: center
+name: demo43_fig1
+---
+As the ball is heavy, friction hardly plays a role allowing to investigate Newton's laws of motion.
+```
+-->
+
 ## Equipment
 * Heavy bowling ball
 * Broomstick 
@@ -38,10 +61,11 @@ Students can gain similar experiences with a heavily loaded supermarket cart. Th
 
 ## Procedure
 During the demonstration, we follow various steps.
+
 **1. Accelerating the bowling ball from rest (with the broom).**\
 You can't accelerate without a broom, the broom has to give you a push.
 
-**2. Stopping a moving bowling ball.\
+**2. Stopping a moving bowling ball.**\
 Without a broom it is difficult or impossible to slow down, the broom has to push you to slow down.
 
 **3. Maintaining constant speed when moving bowling ball.**\
@@ -58,18 +82,11 @@ How do you keep the speed constant during (part of) a circular movement? Only if
 
 The physics teacher can explain this very logically with some vectors, but perhaps this becomes more plausible for students through experiences with the bowling ball.
 
-**7. Try to make a circular motion with the bowling ball at a steady speed. **\
+**7. Try to make a circular motion with the bowling ball at a steady speed.**\
 There is room for discussion here. Let students try it first. Then the question arises in which direction the force must act to go through a bend with constant speed (regardless of direction)? Perpendicular to the direction of movement! One of us did this in the gym where a circle had already been drawn. Everyone tried to hit the ball from the outside of the circle, but one girl had a clever method of raking from it center of the circle.
 
-**8. Try to follow a route like the one in the image above.**
-
-**9. Students work in pairs to formulate the rules about the influence of forces on the movement of the bowling ball.**
-
-**10. Checking students' understanding**\
-Memphis is standing 10 meters in front of the center of an open goal. He receives a hard cross from Bergwijn's left and hits it exactly at right angles, perpendicular to the direction of travel. Explain with a drawing and reasoning why the ball might not go into the goal.
-
 <!-- 
-```{figure} demo43_figure1.png
+```{figure} demo43_figure2.png
 ---
 width: 50%
 align: center
@@ -78,5 +95,14 @@ some caption
 ``` 
 -->
 
+**8. Try to follow a route like the one in the image above.**
+
+**9. Students work in pairs to formulate the rules about the influence of forces on the movement of the bowling ball.**
+
+**10. Checking students' understanding**\
+Memphis is standing 10 meters in front of the center of an open goal. He receives a hard cross from Bergwijn's left and hits it exactly at right angles, perpendicular to the direction of travel. Explain with a drawing and reasoning why the ball might not go into the goal.
+
+
+
 ## Physics background
 Newton's first and second laws are key here: The heavy bowling ball continues straight at a constant speed unless a net force is applied. With the broom you can change both the size and direction and speed of the ball.