Mythbusters: Escape from Alcatraz Part 3

This is Part 3, where they actually "escape". Enjoy!



http://www.youtube.com/watch?v=JNvvPQcw9vg

Mythbusters: Escape from Alcatraz Part 2

Here's Part 2! Part 1 was mostly about the history behind the myth and how Frank Morris and the Anglin brothers actually started smuggling the materials and found a way out of their cells to store the materials. It also showed about the Mythbusters testing the direction the currents would carry the raft. Part 2 is about the Mythbusters building the raft, at the same time cracking jokes about it. Enjoy!




http://www.youtube.com/watch?v=ILu5Ug0lPjk

Mythbusters: Escape from Alcatraz Part 1

This is a Mythbusters special. The myth says that there were three convicts on Alcatraz, Frank Morris and the Anglin brothers, and they built an inflatable raft from over 50 rubber raincoats.

The authorities say that they were headed for Angel Island and some of their personal belongings ended up near there. They were assumed to have drowned.

However, the Mythbusters tested their belief, which was that the inmates were smart enough to have used the tides to get to the Marin Headlands instead.

This is somewhat relevant to Physics as it plays on the principles of wind speed and direction, not to mention density. Admittedly it does not really have much to do with electricity. For that one, I am tracking down the Benjamin Franklin myth.

This is Part 1. I shall post Part 2 and 3 separately. Enjoy!




http://en.wikipedia.org/wiki/MythBusters_(2003_season)#Escape_From_Alcatraz

http://www.youtube.com/watch?v=fZI76hEkZRE

Wet cell battery

We all know about dry cell batteries, which are the normal batteries we use for appliances like clocks, but have you ever heard of a wet cell battery?



Apparently, though this sounds ludicrous it actually is real. A wet cell battery is a battery using chemical reactions to create electrical energy. Its electrolytes are contained in a liquid.



A dry cell battery, on the other hand, has its electrolytes contained in a low-moisture past. Wet cell batteries are used as car batteries as they are inexpensive and rechargable.



So car batteries are wet cell batteries after all.



This is a close-up image of a wet cell battery and its components.












And this is a picture of an actual car battery

http://www.wisegeek.com/what-is-a-dry-cell-battery.htm

http://www.wisegeek.com/what-is-a-wet-cell-battery.htm

http://www.healingtherapies.info/images/Wet_Cell.bmp

http://www.global-b2b-network.com/direct/dbimage/50245303/Car_Battery.jpg

Would you dare to use this toilet?

This picture shows a toilet in the middle of a busy street. Would you dare to use it?

Fortunately, the "glass walls" surrounding the toilet are actually one way mirrors. You can look outside at the busy street, but people outside can only see their own reflections.


Why is this so? When the light concentration on the outside is greater, the one-way mirrors reflect the scene of what is happening outside. However, inside it is darker and therefore the person inside the toilet can look out at the street without being seen.

Be careful though: When night falls and the street outside gets dark, the toilet will become less dark by comparison. If you choose to use the toilet then, it will lead to some rather embarrassing results!

http://loscuatroojos.com/wp-content/uploads/2009/02/one-way-mirror-inside.jpg

Touch Screens and Gloves don't go well together

If you ever try to use a touch screen with a glove on, it will most likely not work. Why is this so? Well, gloves are poor conductors of electricity. The touch screen requires a closed circuit to function. Our bodies are also conductors, and hence when we use our fingers on the touch screen the circuit closes and the touch screen will work. However, since gloves are poor conductors, the
circuit remains open and the touch screen will not work. This is the same for using a stylus. However, it is possible to modify your gloves simply to be able to wear them while using the touch screen. The link below shows how. It is pretty interesting. Have fun!

http://www.instructables.com/id/Making-A-Glove-Work-With-A-Touch-Screen/

Sources:

http://en.wikipedia.org/wiki/Touchscreen#Capacitive

http://en.wikipedia.org/wiki/IPhone#Screen_and_input

Sticky Ice

Why does ice stick to our fingers when we remove it from the fridge? Well, apparently it is due to humidity in the surrounding air. When the surrounding air is wet and humid, your fingers are more moist and the ice will freeze when it comes into contact with the moisture on your fingers. Fortunately, on dryer days your fingers will not be wet and the ice will not stick.

Convection currents

Today Mr. Lim talked about convection currents in class. He posed two questions for us: 1. Since warm air rises and and cold air sinks, will a taller person feel colder than a short person? 2. based on the same concept, will people on the 40th floor feel warmer than on the 15th floor? If yes, why do people claim to feel "cooler" on the uppermost floors?

I think that a tall person would probably feel warmer. This is because they are higher up and the warm air will circle around them. Surprisingly, I have also observed this very often: My taller friends would be sweating profusely, while my shorter friends are huddling together trying to get warm!

As for the second question, I don't think it makes a difference since every level has air-conditioning! As for people feeling "cooler" on the top levels, it is because that is where the cooling unit for the entire building is.

Ice, Water, salt and Ice cream

I have mentioned this very briefly in one of my earlier posts, entitled Measurements and Density. This time, I shall post more about it. Firstly, the density of ice is less than that of water. This is obvious as ice cubes float in a glass of water when you put them in. Simple right? But why is this so? Well, the answer is simple: When water freezes to form ice, it traps air in it. Air is less dense than water, so it causes the ice to float.

Secondly, if a glass is filled with water and ice cubes are placed in the glass, when the ice cubes melt will the water level rise? The answer is no, the water level will NOT rise. At first, I also thought that the water level would rise. However, once I read the explanation, it made perfect sense. The reason is that when ice melts, its volume is still the same so it will take up the same amount of space that it took up when it had not melted yet.

Lastly, we were asked to research on the effects of impurities on water. Well, this is what I know: In cold countries, salt, an impurity, is thrown on the roads to melt the snow and ice. This is because impurities lower the melting point of ice. This same concept is applied to make ice cream. You can just pour sugar and milk into a freezer bag and seal it, then place it into a larger bag, already filled with crushed salt. Make sure both bags are tightly sealed, and then shake the bags vigorously(but not so vigorously that they split open or smash!) After some time, the contents should solidify and turn into delicious homemade ice cream!

I found a video on Youtube summarising the above instructions in a 1min 18 sec clip. Enjoy!

http://www.elmhurst.edu/~chm/vchembook/122densityice.html

http://sg.answers.yahoo.com/question/index;_ylt=AqAdCXkAnMkY8xceJjXqoAQh4wt.;_ylv=3?qid=20080208133726AAWySCd

http://www.wikihow.com/Make-Ice-Cream

Challenger disaster

I read about this and decided to post it, not just because it is related to thermal physics, it also shows how ignorant Man is.

On January 28, 1986, the Challenger was supposed to conduct the TISP (Teacher in Space Program). In other words, for the very first time, a teacher would be boarding the Challenger to visit space. However, the temperature was too cold (29 degrees F). The engineers who made the Challenger told the NASA managers that they should wait until the temperature reached 58 degrees F. This is because the low temperatures might cause the O-rings to not seal properly. The O-rings kept hot gases, preventing them from escaping.

However, NASA really wanted to launch the flight, so the managers decided to give the go-ahead anyway. Just as Challenger was pulling away from Earth, one of the O-rings failed to seal, causing the hot gas to escape. Flames shot out from one slide of the rocket and licked at the hydrogen tank. Seconds later, the tank exploded, and all seven crew members, including the teacher, died on the spot.

This shows how important it is to consider the safety facts instead of rushing into things. Due to the cold weather, the O-ring had contracted and became too stiff to seal properly. This caused 7 innocent people to be killed.

This is a video showing the live recording of the Challenger explosion.

Centre of Gravity

I found out several things about the centre of gravity. Firstly, the centre of gravity is at the middle of things, in other words, at the very core of the object. Also, it is what causes things to balance themselves. The first time the concept of the centre of gravity was brought up was when Archimedes used this concept to explain the balance and lack of resulting moment when two objects are balanced in a specific way. Hence, if you have a sphere, its centre of gravit would be at the core. This is also why it is harder for spheres to balance: they have considerably smaller cores and less centre of gravity.

http://en.wikipedia.org/wiki/Center_of_mass

The Upside Down World Map

I've always wondered about the Earth. I mean, the Earth is a sphere, so wouldn't that mean that people at the South Pole and at the bottom half of the Earth are standing upside down? I know that the reason why they don't fall off is gravity, but wouldn't they feel weird standing upside down? I asked my dad, and he said that although theoratically half the Earth's inhabitants are "upside down" at any one time, nobody looks upside down because to them, their half of the Earth is the right way up and the other half is upside down!


Then, he showed me this "upside down worlds map" made in Australia. Australia is known as Down Under because it is, according to the world, near the bottom of the Earth. However, in this map, Australia is challenging this. This world map, as its name suggests, has Antarctica and Australia at the top of the world and South America on top of North America. It shows another way of looking at the Earth. Cool, isn't it?


This picture is kind of small, but you can click on it to view a page where it is much, much, much larger. Enjoy!

The North Pole Issue

Today we talked about gravity and the North Pole. I did a bit more research and found out that although both poles have more gravity than the other parts of the Earth, the North actually has more gravitational pull than the South as Antartica is the Southern continent and it is a very high plateau so it would be higher up and consequently have less gravity than the North, which is in the middle of a deep ocean. This is also the same reason why the South is colder than the North. Hence, Mr. Lim was wrong to say that the North Pole has equal gravity to the South Pole.

This is the site where I did my research. http://sg.answers.yahoo.com/question/index;_ylt=AkNOnOfUtpM8NsVKD_Nlolwh4wt.;_ylv=3?qid=20070726222930AAUa3Hd

Forces at Work

Hi guys, I found this cool video on forces. Enjoy!

Forces

We discussed forces in class today. Mr. Lim gave us a question to chew on: If there is an object of weight 1N on the ground, and a force of 1 N is applied to lift it, will the object be able to be lifted into the air? My theory is that it will not be lifted. This is because there is an equal force acting on both sides of the object, namely, upwards lift and downwards weight. Hence, the object will not move.


Take this picture as an example. The four forces are acting on it with equal strength. Hence, the box does not move. If you look at FN and Fg, they are the two forces we are focusing on. The box is neither moving up nor down, hence the equal forces have no effect on it and the box is not being lifted.

Quicksand

Today Mr. Lim told us to research on quicksand in relation to the formula Pressure=Force divided by Area. According to Wikipedia, Quicksand is a non-Newtonian liquid. That means that the liquid seems solid when untouched but when stepped on it quickly becomes a liquid and then quickly solidifies around you again. This is because the pressure applied causes the person to slowly sink down. However, if a person applies enough force and is quick enough, it is even possible to walk on quicksand or other such liquids.

The same concept is applied with trying to get out of quicksand. You have to slowly and methodically move about towards the edge or something to grab onto. By keeping calm and not panicking, and taking deep breaths, you remain bouyant. Although it is a long and tedious process, you willl eventually be able to get out.

Meniscus 2 (Follow Up)

I have managed to find the definition of surface tension. Surface tension is what causes the surface portion of liquid to be attracted to another surface. Based on this, I infer that polar molecues attraction is caused by surface tension. That's one question answered.

As for the other question... I suppose it would be very hard to even test it, as non-polar materials are likely to be opaque, and hence the result cannot be observed. However, if the theories are correct, liquids should not form a meniscus of any sort when they are placed in a container made of a non-polar material.

Meniscus

I researched on meniscus and found many answers, mostly too scientifc ones. However, I finally managed to come across a clear but simple explanation. There are two websites which I got my answer from.

Basically, water has polar molecues, just like glass. Polar molecuse tend to stick togther, so the water sticks to the edge of the measuring cylinder. Hence, the water will tend to form a curve and creep up the edge of the cylinder. This will result in the formation of a concave meniscus, as depicted in A. A convex meniscus, depicted in B, is very rare but may be formed by liquids like mercury where the molecules of the liquid have a stronger attraction to each other than to the container.

What I'm wondering is, if a cylinder of a different material is used, will it also form a meniscus and why? Surely not all material have polar molecues? And what does surface tension have to do with this?

These are the websites that I used for my research.

http://en.wikipedia.org/wiki/Meniscus

http://answers.yahoo.com/question/index?qid=20080917134724AArrlg8

Measurements and density

Today, Mr. Lim wrapped up the topic on Measurements and Units. He also went through the class assignment on IVLE with us. At the end, he gave us two questions to think about. The first was: There is a beaker of liquid with a density of A grams/cubic cm. A represents any natural number. There is also a solid that cannot be dissolved at the exact same density. Where in the beaker of liquid will it be? At the surface, in the liquid or at the bottom of the beaker?

In my opinion, this question is no practical as no two substances are identical. Each substance is unique and hence no two substances have the same density. Even ice and water, different states of the same substance, have different densitieas ice is less dense than water. Hence, this is not likely to happen.

However, in the event that it does happen by a stroke of luck... If it were a liquid, both liquids would mix together and form a mixture. However, since it is a solid, perhaps it would be in the liquid itself as that is the closest it gets to mxing. Also, to float would mean it is less dense and to sink would mean it is denser, so it would probably be in between.

The second question is as follows: Water always has a meniscus at the suface where it curves instead of being fully straight. Why? Even Mr. Lim is not too sure but he says it has something to do with surface tension. I think it is because air is pressing against the surface of water, causing it to bend and curve slightly. I shall research more on this subject when I have time.

Scenario Presentation 2

We had the rest of the scenario presentations. There were 3 groups left. The first group had this scenario: In a production line, 10000 small screws are to be sorted into packs of 50 each. Manual counting would be too tedious. Suggest ways in which the sorting may be done.

This problem seems quite tricky. However, if you think hard about it, the solution is actually pretty simple.


The group had two solutions. 1. Use an electromagnet. Adjust the resistance of the electromagnet such that it attracts 50 screws each time. However, Mr. Lim said that this solution was not very relevant as the electromagnet would be likely to attract either all the screws or none at all. Hence, this solution was not likely to work.


2. Use a weighing scale. Count the first 50 screws and weigh them. Subsequently, grab a handful of screws and weigh them. Compare the reading to the first reading of 50 screw and adjust the number of screws accordingly. This solution is both practical and feasible. It is based on how shopkeepers weigh biscuits or ham using the weighing scale and add more or take out some based on the weight of the products.


The next group had a relatively more common scenario, but explaining it was more difficult. This was their problem: A spring balance will give a different reading on the Moon than from that on Earth. A beam balance, however, will give the same reading. Explain why.


The group's answer is as follows: A spring balance measures weight, which is dependant on gravity. The Moon has less gravity than the Earth, hence the reading differs. However, a beam balance measures mass, which is constant no matter what. Short and sweet, but very clear.


The final group had a very interesting topic. How do submarines float and sink at will?


In my opinion, this group had the most detailed presentation. They explained how air is pumped into the ballast tanks to force water out so that the submarine would float. On top of that, they included a lot of other information such as diagrams, and information on the Kursk Russian submarine disaster. They talked about how a faulty Dummy torpedo had allowed flammable liquid to leak through and explode the front of the submarine, letting water in and causing the submarine to sink.

At the end of the presentation, they gave us question to think about: If a submarine sinks to the seabed, why is it no longer available to move off? The answer is that there is no water under the submarine to create a lift force, hence the submarine is stuck there until rescue workers drop a rope down to haul it back up. I enjoyed this group's presentation the most.

I enjoy thought-provoking lessons and topics like the ones Mr. Lim gave us. I hope we'll be able to have more of such lessons in the future.