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
Thursday, February 26, 2009
Sunday, February 22, 2009
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!
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!
Thursday, February 12, 2009
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
This is the site where I did my research. http://sg.answers.yahoo.com/question/index;_ylt=AkNOnOfUtpM8NsVKD_Nlolwh4wt.;_ylv=3?qid=20070726222930AAUa3Hd
Monday, February 9, 2009
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.
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.
Thursday, February 5, 2009
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.
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.
Wednesday, February 4, 2009
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.
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.
Tuesday, February 3, 2009
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
Monday, February 2, 2009
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.
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.
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