I'm not sure whether it is related to density but i found it rather interesting to watch.
The gas is called sulfur hexafluoride and it is denser than the surrounding air.
Hope you like it.>_<
Saturday, February 28, 2009
center of gravity in pendulum bob
Well, for this question,i did some research but it was futile in the end but i got a rough idea where the gravity is through the pictures i came across.The gravity in the pendulum is located in the middle of the bob. The reason should be that if the gravity is located in the middle of the bob, there would be equal amount of gravitational force acting on it.
As you can see from this animation, the velocity [V] and the acceleration vectors [A] is all acting on the middle of the pendulum.So as to conclude, the location of the gravity of the pendulum is in the middle of the bob.
Another question that was asked was where is the center of gravity when the plasticine is placed on top of it or wrapped around it.The center of gravity in this case is still the same as the pendulum did not changed but only one variable is added which is the plasticine.The center of gravity would still be the same apart from the amount of gravity as it would be heavier and thus, maybe more gravity acting/applied on it.
Thursday, February 19, 2009
Archimedes of Syracuse
Full name : Archimedes of Syracuse
Birth : c. 287BC
Death : c. 212 BC
Birth and death place : Syracuse, Sicily, Magna Graecia
Main Interest : mathematics, physic, engineering, astronomy, invention
Birth : c. 287BC
Death : c. 212 BC
Birth and death place : Syracuse, Sicily, Magna Graecia
Main Interest : mathematics, physic, engineering, astronomy, invention
WHAT HE FOUND OUT:
1.The Archimedes Screw. Archimedes had invented / found out the screw which is normally used to transfer water.
2. The claw of Archimede
3.The Archimedes Heat Ray
4.Levers
5. Improving the power and accuracy of a caltapult
6.Used the method of exhaustion to find out the approximate value of TT
this is one other thing he found out but i don't know what it is called.
GOLD or PLATINUM which is denser?
Today in school, Mr Lim thinks that GOLD is the densest of all but in the table in our school's textbooks states that platinum is denser than gold but he still thinks that gold is still denser.After much research, I still found out that platinum is heavier than gold and the heavier it is, the denser it would be. So what exactly is the answer-which is denser? Platinum or gold?
Platinum is usually 24 karat, which is 100% gold while Gold is only 18 karat, which is 75% gold and that proves that platinum is truly heavier than gold. It is also stated that platinum is an extremely rare metal which is 60% heavier than gold.
So..I assume that Mr Lim is wrong in the sense that saying gold is denser than platinum.
No worries! d:) everybody makes MISTAKES!
References:
http://www.firenzejewels.com/white-gold-vs-platinum.html
Platinum is usually 24 karat, which is 100% gold while Gold is only 18 karat, which is 75% gold and that proves that platinum is truly heavier than gold. It is also stated that platinum is an extremely rare metal which is 60% heavier than gold.
So..I assume that Mr Lim is wrong in the sense that saying gold is denser than platinum.
No worries! d:) everybody makes MISTAKES!
References:
http://www.firenzejewels.com/white-gold-vs-platinum.html
Sunday, February 15, 2009
QUESTION that was asked
The question that was asked was whether an object of 1N would stop when a force of 1N acted on it at the end of the path.
The answer should be NO as an object cannot stop abruptly when a force is acting on it. Example:You are running at a high speed.Another person is at the end of the road waiting to stop you with the same force which was produced by the person who push you.You would obviously slow down to a halt when you a forced to stop - you can't immediately stop right?
The answer should be NO as an object cannot stop abruptly when a force is acting on it. Example:You are running at a high speed.Another person is at the end of the road waiting to stop you with the same force which was produced by the person who push you.You would obviously slow down to a halt when you a forced to stop - you can't immediately stop right?
Saturday, February 14, 2009
why is gravity stronger on the NORTH POLE?
The 
earth is slightly flattened at the poles, the poles are a bit closer to the center of the earth than land on the equator, so the earth is not circle but sphere.Due to this reasoning, the North pole and South pole is closer to the core and the other lands are a bit further.The South pole is in Antarctica which is a very high plateau.So the gravity there would be less as compared to that in the North pole. The Earth is slightly flattened at the the North pole, which is in the middle of a deep ocean.The South pole is a continental which tends to be about 50km thick, while the North pole tends to be about 3 km thick.
earth is slightly flattened at the poles, the poles are a bit closer to the center of the earth than land on the equator, so the earth is not circle but sphere.Due to this reasoning, the North pole and South pole is closer to the core and the other lands are a bit further.The South pole is in Antarctica which is a very high plateau.So the gravity there would be less as compared to that in the North pole. The Earth is slightly flattened at the the North pole, which is in the middle of a deep ocean.The South pole is a continental which tends to be about 50km thick, while the North pole tends to be about 3 km thick.Reference:
how to get out of quicksand
Continual from quicksand:
How to get out of quicksand.
- Drop everything-your body is less dense than quicksand.you would sink if you are weighed down by something heavy.Take off your back bag, shoes,etc anything heavy .
- Relax-your body's buoyancy will cause you to float.Do not struggle or panic.
- Breathe deeply-it would calm you and it would make you more buoyant.Keep as much air as possible it would be more difficult to sink , you would "float".
- Get on your back-the more you spread your weight, the harder it will be to sink.Once your legs are free, slowly propel yourself to land or if you are near the land, roll yourself.
- Take your time-frantic movements will only loosen the sand. Quicksand can react unpredictably to your movements and if you move slowly, you can stop an adverse reaction.
- Get plenty of rest-be sure to take breaks and float on your back to prevent you from exhaustion.
Always bring a long stick with you when on this types of trips.Unknowingly, you even might find it useful!
terminal velocity
A
falling object achieves its terminal velocity when the downward force of gravity (Fg) equals the upward force of drag (Fd).
As the object accelerates (usually downwards due to gravity), the drag force acting on the object increases. At a particular speed, the drag force produced will equal the object's weight (mg). Eventually, it plummets at a constant speed called terminal velocity (also called settling velocity). Terminal velocity varies directly with the ratio of drag to weight. More drag means a lower terminal velocity, while increased weight means a higher terminal velocity. An object moving downward with greater than terminal velocity (for example because it was affected by a downward force or it fell from a thinner part of the atmosphere or it changed shape) will slow until it reaches terminal velocity
To better understand this,terminal velocity is also called instantanous speed / speed at any point of time.
Feel free to correct me about this. Not too sure
falling object achieves its terminal velocity when the downward force of gravity (Fg) equals the upward force of drag (Fd).As the object accelerates (usually downwards due to gravity), the drag force acting on the object increases. At a particular speed, the drag force produced will equal the object's weight (mg). Eventually, it plummets at a constant speed called terminal velocity (also called settling velocity). Terminal velocity varies directly with the ratio of drag to weight. More drag means a lower terminal velocity, while increased weight means a higher terminal velocity. An object moving downward with greater than terminal velocity (for example because it was affected by a downward force or it fell from a thinner part of the atmosphere or it changed shape) will slow until it reaches terminal velocity
To better understand this,terminal velocity is also called instantanous speed / speed at any point of time.
Feel free to correct me about this. Not too sure
Standard deviation
This is related to the average question.If taking the average is good enough, what about STANDARD DEVIATION?The concept of standard Deviation is more difficult or complicated than other types of concepts.*FROM ALL THE CONCEPTS I KNOW* At this age, we would never use the words, standard deviation but that doesn't mean that we do not try to understand the concept behind it.
In order to understand this concept,we would first learn about what scientist call normal distribution of data.
It means that most examples in a data are close to average while some examples tends to be extreme.
Example: you are writing a report on nutrition and you need to look at people's daily calorie consumption. Like most data, the numbers for people's typical consumption will turn out to be normally distributed-close to mean while fewer people would tend to overeat or eat less than the mean.
Why is this useful? Here's an example: If you are comparing test scores for different schools, the standard deviation will tell you how diverse the test scores are for each school.
Let's say Springfield Elementary has a higher mean test score than Shelbyville Elementary. Your first reaction might be to say that the kids at Springfield are smarter.
But a bigger standard deviation for one school tells you that there are relatively more kids at that school scoring toward one extreme or the other. By asking a few follow-up questions you might find that, say, Springfield's mean was skewed up because the school district sends all of the gifted education kids to Springfield. Or that Shelbyville's scores were dragged down because students who recently have been "mainstreamed" from special education classes have all been sent to Shelbyville.
Friday, February 13, 2009
austronauts
How go astronauts go the bathroom in space?
In the toilet, there is still no gravity so, crew member must use foot restraints, a seat belt and handholds to remain seated.The toilet has a fan that draws solid wastes to a compartment where they are dried and disinfected.
Early spacecraft used diapers and disposable bags for astronaut elimination while astronauts in spacesuits of today, uses diapers.Solid wastes are compressed and stored on-board, and then removed after landing.
Waste water is vented to space, although future systems may recycle it and the air is filtered to remove odor and bacteria.
Astronauts brush their teeth just like they do on Earth. There is no shower on the Shuttle, so astronauts must make do with sponge baths until they return home.
The urine collection system was also improved. A newer type of fan system is being used to force the urine to a holding tank where it is periodically ejected into space, where it vaporizes.
Wow! I never thought that leaving in a spacecraft could be that interesting.It would be my wishful part of thinking if I could ever try this out on land.Even if there is, I think I have to travel all the way round the Earth just to try it.Perhaps eventually I might have a chance!
me and my astronauts
In the toilet, there is still no gravity so, crew member must use foot restraints, a seat belt and handholds to remain seated.The toilet has a fan that draws solid wastes to a compartment where they are dried and disinfected.
Early spacecraft used diapers and disposable bags for astronaut elimination while astronauts in spacesuits of today, uses diapers.Solid wastes are compressed and stored on-board, and then removed after landing.
Waste water is vented to space, although future systems may recycle it and the air is filtered to remove odor and bacteria.
Astronauts brush their teeth just like they do on Earth. There is no shower on the Shuttle, so astronauts must make do with sponge baths until they return home.
The urine collection system was also improved. A newer type of fan system is being used to force the urine to a holding tank where it is periodically ejected into space, where it vaporizes.
Wow! I never thought that leaving in a spacecraft could be that interesting.It would be my wishful part of thinking if I could ever try this out on land.Even if there is, I think I have to travel all the way round the Earth just to try it.Perhaps eventually I might have a chance!
me and my astronauts
Monday, February 9, 2009
principle of moment
Torque is the tendency of a force to rotate an object about an axis(or fulcrum or pivot). Just as a force is a push or a pull, a torque can be thought of as a twist.
The symbol for torque is τ.
Torque is also called moment or moment of force. This should neither be confused with the various other definitions of "moment" in physics nor with "momentum".
In the context of mechanical engineering, the terms "moment" and "torque" are not necessarily interchangeable; rather, one or the other may be preferred in a specific context.
For example, "torque" is usually used to describe a rotational force down a shaft, for example a turning screw-driver, whereas "moment" is more often used to describe a bending force on a beam.
Frankly speaking, I still don't know what is the principle of moment but I think I get a brief idea of what it is about.
More on : http://en.wikipedia.org/wiki/Torque
The symbol for torque is τ.
Torque is also called moment or moment of force. This should neither be confused with the various other definitions of "moment" in physics nor with "momentum".
In the context of mechanical engineering, the terms "moment" and "torque" are not necessarily interchangeable; rather, one or the other may be preferred in a specific context.
For example, "torque" is usually used to describe a rotational force down a shaft, for example a turning screw-driver, whereas "moment" is more often used to describe a bending force on a beam.
Frankly speaking, I still don't know what is the principle of moment but I think I get a brief idea of what it is about.
More on : http://en.wikipedia.org/wiki/Torque
average
Why do we need to take the average?
Well according to yours truly, so that we can ensure the accuracy of the experiment.If we to have to use the exact calculation, imagine the amount of numbers we have to remember.So if you were to calculate the average, won't it actually save a lot of hassle.
Well according to yours truly, so that we can ensure the accuracy of the experiment.If we to have to use the exact calculation, imagine the amount of numbers we have to remember.So if you were to calculate the average, won't it actually save a lot of hassle.
concave or convex meniscus
A = concave menisus. B = convex meniscus.
A convex meniscus occurs when the molecules have a stronger attraction to each other than to the container.
A concave meniscus occurs when the molecules of the liquid attract those of the container
A concave meniscus occurs when the molecules of the liquid attract those of the container
liquefaction
Today, we were told that liquefaction has something to do with quicksand and this was what I found.
Liquefaction:
When the soil is loaded,it would suddenly go firm solid state to liquefied state.
It is likely to occur in loose to moderate granular soil-sols that are able to crumble easily,with poor drainage.
this is a video about liquefaction which commonly occur in earthquakes.sorry about the clarity of the video-couldn't get a HD video which is the same as this.Uring the first part of the video if you were to 'strain' your eyes, you actually could see bubbles coming out of the g.round
Liquefaction:
When the soil is loaded,it would suddenly go firm solid state to liquefied state.
It is likely to occur in loose to moderate granular soil-sols that are able to crumble easily,with poor drainage.
Loose sands, which go from a solid state to have the consistency of a heavy liquid, or reach a liquefied state as a consequence of increasing pore water pressures, and thus decreasing effective stress(pressure), induced by their tendency to decrease in volume when subjected to cyclic undrained loading.
It is often found along riverbeds, beaches, dunes, and areas where windblown silt and sand have accumulated.
this is a video about liquefaction which commonly occur in earthquakes.sorry about the clarity of the video-couldn't get a HD video which is the same as this.Uring the first part of the video if you were to 'strain' your eyes, you actually could see bubbles coming out of the g.round
Thursday, February 5, 2009
Quick sand
Quick sand is not really a special type of sand, it is actually a condition that is happening to the sand.
There is an insistent flow of water beneath the surface, often an underground spring, that weakens them and thus, lifting the grains apart.
Each grain of sand is surrounded by a thin film of water and as they lose friction with each other, the solid mass breaks asunder.
The water is not strong enough to completely disperse the sand and the resultant soupy pool therefore can look like solid ground.
Good places to find quicksand are on ocean coasts, near sandy creek beds and area of sand over an impervious clay substructure.
Another good place to find quicksand is in hilly country with abundant caves and underground springs lurking beneath.
Most patches of quicksand are only a few inches to several feet deep. And quicksand does not pull its victim down to lethal depths like a deranged Hoover. It is, however, possible to perish in quicksand but you really have to work at it.
Should you stumble into quicksand you will sink just as you sink in water. If the quicksand is shallow, you can retrace your steps and extricate yourself from the sandy tentacles.
But if the quicksand is deeper there is still little to worry about. Since the water is slightly more dense than than the human body it is possible to float in quicksand.
In fact, since quicksand is saturated with liquid it is far heavier than water and will allow you to float even higher, provided you move slowly and allow the sandy potion to flow under your body.
Newton's 3 laws of motion
Newton's laws:I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
Meaning ---->an object that has a constant speed tends to remain the same speed until a force is applied to it.
II. The relationship between an object's mass (m), its acceleration (a), and the applied force (F) is F = ma. Acceleration and force are vectors (as indicated by their symbols); in this law the direction of the force vector is the same as the direction of the acceleration vector.
Meaning---->f = ma
III. For every action there is an equal and opposite reaction.
Meaning---->This law is exemplified by what happens if we step off a boat onto the bank of a lake: as we move in the direction of the shore, the boat tends to move in the opposite direction.
Tuesday, February 3, 2009
Greenwich Meidian Time
This is a picture of the Royal Observatory in Greenwich.Greenwich Meidian Time:
Greenwich, England has been the home of Greenwich Mean Time (GMT) since 1884. GMT is sometimes called Greenwich Meridian Time because it is measured from the Greenwich Meridian Line at the Royal Observatory in Greenwich. Greenwich is the place from where all time zones are measured.
GMT is World Time and the basis of every world time zone which sets the time of day and is at the centre of the time zone map. GMT sets current time or official time around the globe. Most time changes are measured by GMT. Although GMT has been replaced by atomic time (UTC) it is still widely regarded as the correct time for every international time zone.
Greenwich Mean Time is international time, the basis of the world time clock. GMT marks precision time and military time (sometimes called Zulu Time). Defines date and time and the exact time. The atomic time clock is adjusted by leap seconds to maintain synchronicity with GMT.
Conversion
100 cm= 1m
100cm x 100cm= 10 000 cm2
10 000 cm2 = 1m2
In my opinion cm3 and m3 is :
1m3 = 1m x 1m x 1m (1,000,000 cm3)
1cm3= 1cm x 1cm x 1cm
100cm x 100cm= 10 000 cm2
10 000 cm2 = 1m2
In my opinion cm3 and m3 is :
1m3 = 1m x 1m x 1m (1,000,000 cm3)
1cm3= 1cm x 1cm x 1cm
spring balance and beam balance
A spring balance will give a different mass reading on the Moon from that on Earth. A beam balance however, will give the same reading.Explain why.
Beam Balance:
Beam balance measures mass.
Mass is the amount of matter the object has.
The S.I. unit of mass is kg
Spring Balance:
Spring balance measures weight not mass.
Disadvantage: It requires gravity to measure.
The S.I. unit of weight is newton (N).
That is why when we are in outer space, we become lighter-there is less gravity!
Mass remains constant while weight is dependent on the gravitational pull of the planet. Mass only changes with a change in matter that results in a change of volume.
~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~
Mass remains constant throughout. Only weight changes with gravitational acceleration. Mass will only change with a change in the volume of matter in the body.
dENSITY
This was a question asked today: What happens when the density of a solid object is the same as the density of the liquid,will it float or will it sink ?
Example: the solid has a density of A g/cm3 and the density of the liquid is also A g/cm3.
The answer to whether it would float or sink is...
The solid should not be floating or sinking but instead suspended in the middle of the liquid.
4. copper wire
You are given a length of copper wire with a small diameter. The only measurement you have is a metre ruler.how do you measure the diameter of the ruler as accurately as you can.
The solution is simple.Firstly, twirl the copper wire around a pencil as tightly as possible. (leaving no gaps in between each coil) Measure the length of the pencil covered by the wire and count the number of coils round the pencil. Divide the length of the pencil by the number of coils. 'Ta Da' ! Isn't it easy?!?!?!
Subscribe to:
Posts (Atom)