Quicksand



What is quicksand? And how to escape from it...

The thought of quicksand often inspires fear in people, since many believe that being caught in quicksand will quickly result in drowning. This is actually not the case. People are lighter than quicksand, and if they do not struggle, they will quickly rise to the top. Further quicksand is just ordinary sand, but it can cause one to sink because it has become oversaturated with water.
Quicksand can occur anywhere in the world but is most likely to occur near a water source, like a creek, river, ocean or lake. When the sand gets a little exposure to water, it actually becomes more finely packed. A little bit of water increases friction in the sand, causing it to bind closely together. This is why people tend to use water when building sand castles, as the water helps maintain the shapes.
However, too much water causes the sand particles to lose friction, and lack of friction means the sand is quicksand. Sand slips apart rapidly when weight is put onto it, as a person stepping on it might do. Hence the term quicksand applies to sand that quickly allows one to sink into it.
Portrayals of quicksand are highly exaggerated, though. People only tend to drown in quicksand if they flail their arms and legs about. This makes them sink because they are literally helping the quicksand split apart. On the other hand, the person who does not panic, and who puts one’s hands and legs slightly apart, moving as slowly as possibly, will not sink under the quicksand. As in water, people are naturally buoyant in quicksand.
Further, quicksand is not a bottomless pit that will suck one down to the earth’s core. In fact, some quicksand is only about two to four feet (about .61-1.22m) deep. This depth can cause some difficulty when one tries to get out. One may notice sometimes it’s a lot easier to get into water, than to get out of water. This is because the density of the water or of quicksand creates a vacuum-like effect. Again the key is moving very slowly in order to get out of the quicksand.
Sometimes quicksand causes problems when it forms under buildings, which have far greater mass than a single person. In times of flooding over sand, theoretically, regular sand could become quicksand, and cause the mass of a building to sink. This sinking might also cause structural instability in the building and precipitate collapse, particularly in instances of earthquakes.
However, the individual need not fear quicksand if he or she remembers “quick sand, slow movement.” Even a person falling headfirst into quicksand is likely to float to the surface quite rapidly if he or she does not struggle.

Taken from: http://www.wisegeek.com/what-is-quicksand.htm

Why does not struggling in quicksand work?
Not struggling and lying flat makes your area bigger.
The bigger the area, force constant, pressure is lower...
The smaller the area, force constant, pressure is lower...
Lying flat makes your area bigger and pressure is lower so you will not sink, but instead, float back up :D
However, struggling, will make your area smaller and pressure is higher, causing you to sink even faster.

GMT aka Greenwich Meridian Time

Average

What is average?

Average is the middle of the numbers that are being compared...acording to the dictionary, it is the result obtained by adding several numbers together and then dividing the total by the number of amounts.

Eg. The average of 30, 40, 25 and 35 is 32.5. I added the numbers together and divided by the amount of numbers, which is (30+40+25+35) / 4 = 32.5 :D

Why do we need to take average?

I feel that we have to take average to be more fair or accurate.
Example: I ran a round around the track with a timing of 50 seconds. The next round I ran, I took 1 minute. After another round, I took 1 minute and 25 seconds. What is the average time I took?
Answer: 1 minute 5 seconds.

Why do I want to find th average?
I would like to find the average of the run to estimate how long I took for each round.

Meniscus




A: Concave Meniscus
B: Convex Meniscus

Meniscus, plural: menisci, from the Greek for "crescent", is a curve in the surface of a liquid and is produced in response to the surface of the container or another object. It can be either concave or convex. A convex meniscus occurs when the molecules have a stronger attraction to each other than to the container. This may be seen between mercury and glass in barometers. Conversely, a concave meniscus occurs when the molecules of the liquid attract those of the container. This can be seen between water and glass. Capillary action acts on concave menisci to pull the liquid up, and on convex menisci to pull the liquid down. This phenomenon is important in transpirational pull in plants. Honey, water, milk etc. have a lower meniscus. When a tube of a narrow bore, often called a capillary tube, is dipped into a liquid and the liquid “wets” the tube (with zero contact angle), the liquid surface inside the tube forms a concave meniscus, which is a virtually spherical surface having the same radius, r, as the inside of the tube. The tube experiences a downward force of magnitude 2πrdσ. Mercury etc. have an upper convex meniscus.
When reading a scale on the side of a container filled with liquid, the meniscus must be taken into account in order to obtain a precise measurement. Manufacturers take the meniscus into account and calibrate their measurement marks relative to the resulting meniscus. The measurement is taken with the meniscus at eye level to eliminate parallax error, and at the central point of the curve of the meniscus, i.e. the top of the meniscus, in the unusual case of a liquid like mercury, or more usually, the bottom of the meniscus in water and most other liquids.





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

Density




Question: When the solid is out into the liwuid, both of same density, will the solid float, sink or...?

Is it A, B or C ?

My Hypothesis: I guess that it will be at B.
My Reason: Since it is the same density, it will neither sink nor float, so it will remain in the middle.

According to research...to me, some of the information will be understood only if you went to the website...

...Methods depending on the free suspension of the solid in a liquid of the same density have been especially studied by Retgers and Gossner in view of their applicability to density determinations of crystals. Two typical forms are in use; in one a liquid is prepared in which the crystal freely swims, the density of the liquid being ascertained by the pycnometer or other methods; in the other a liquid of variable density, the so-called "diffusion column," is prepared, and observation is made of the level at which the particle comes to rest. The first type is in commonest use; since both necessitate the use of dense liquids, a summary of the media of most value, with their essential properties, will be given...

Taken from: http://www.1911encyclopedia.org/Density

Quicksand



What is quicksand? And how to escape from it...

The thought of quicksand often inspires fear in people, since many believe that being caught in quicksand will quickly result in drowning. This is actually not the case. People are lighter than quicksand, and if they do not struggle, they will quickly rise to the top. Further quicksand is just ordinary sand, but it can cause one to sink because it has become oversaturated with water.
Quicksand can occur anywhere in the world but is most likely to occur near a water source, like a creek, river, ocean or lake. When the sand gets a little exposure to water, it actually becomes more finely packed. A little bit of water increases friction in the sand, causing it to bind closely together. This is why people tend to use water when building sand castles, as the water helps maintain the shapes.
However, too much water causes the sand particles to lose friction, and lack of friction means the sand is quicksand. Sand slips apart rapidly when weight is put onto it, as a person stepping on it might do. Hence the term quicksand applies to sand that quickly allows one to sink into it.
Portrayals of quicksand are highly exaggerated, though. People only tend to drown in quicksand if they flail their arms and legs about. This makes them sink because they are literally helping the quicksand split apart. On the other hand, the person who does not panic, and who puts one’s hands and legs slightly apart, moving as slowly as possibly, will not sink under the quicksand. As in water, people are naturally buoyant in quicksand.
Further, quicksand is not a bottomless pit that will suck one down to the earth’s core. In fact, some quicksand is only about two to four feet (about .61-1.22m) deep. This depth can cause some difficulty when one tries to get out. One may notice sometimes it’s a lot easier to get into water, than to get out of water. This is because the density of the water or of quicksand creates a vacuum-like effect. Again the key is moving very slowly in order to get out of the quicksand.
Sometimes quicksand causes problems when it forms under buildings, which have far greater mass than a single person. In times of flooding over sand, theoretically, regular sand could become quicksand, and cause the mass of a building to sink. This sinking might also cause structural instability in the building and precipitate collapse, particularly in instances of earthquakes.
However, the individual need not fear quicksand if he or she remembers “quick sand, slow movement.” Even a person falling headfirst into quicksand is likely to float to the surface quite rapidly if he or she does not struggle.

Taken from: http://www.wisegeek.com/what-is-quicksand.htm

Why does not struggling in quicksand work?
Not struggling and lying flat makes your area bigger.
The bigger the area, force constant, pressure is lower...
The smaller the area, force constant, pressure is lower...
Lying flat makes your area bigger and pressure is lower so you will not sink, but instead, float back up :D
However, struggling, will make your area smaller and pressure is higher, causing you to sink even faster.

GMT aka Greenwich Meridian Time

Average

What is average?

Average is the middle of the numbers that are being compared...acording to the dictionary, it is the result obtained by adding several numbers together and then dividing the total by the number of amounts.

Eg. The average of 30, 40, 25 and 35 is 32.5. I added the numbers together and divided by the amount of numbers, which is (30+40+25+35) / 4 = 32.5 :D

Why do we need to take average?

I feel that we have to take average to be more fair or accurate.
Example: I ran a round around the track with a timing of 50 seconds. The next round I ran, I took 1 minute. After another round, I took 1 minute and 25 seconds. What is the average time I took?
Answer: 1 minute 5 seconds.

Why do I want to find th average?
I would like to find the average of the run to estimate how long I took for each round.

Meniscus




A: Concave Meniscus
B: Convex Meniscus

Meniscus, plural: menisci, from the Greek for "crescent", is a curve in the surface of a liquid and is produced in response to the surface of the container or another object. It can be either concave or convex. A convex meniscus occurs when the molecules have a stronger attraction to each other than to the container. This may be seen between mercury and glass in barometers. Conversely, a concave meniscus occurs when the molecules of the liquid attract those of the container. This can be seen between water and glass. Capillary action acts on concave menisci to pull the liquid up, and on convex menisci to pull the liquid down. This phenomenon is important in transpirational pull in plants. Honey, water, milk etc. have a lower meniscus. When a tube of a narrow bore, often called a capillary tube, is dipped into a liquid and the liquid “wets” the tube (with zero contact angle), the liquid surface inside the tube forms a concave meniscus, which is a virtually spherical surface having the same radius, r, as the inside of the tube. The tube experiences a downward force of magnitude 2πrdσ. Mercury etc. have an upper convex meniscus.
When reading a scale on the side of a container filled with liquid, the meniscus must be taken into account in order to obtain a precise measurement. Manufacturers take the meniscus into account and calibrate their measurement marks relative to the resulting meniscus. The measurement is taken with the meniscus at eye level to eliminate parallax error, and at the central point of the curve of the meniscus, i.e. the top of the meniscus, in the unusual case of a liquid like mercury, or more usually, the bottom of the meniscus in water and most other liquids.





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

Density




Question: When the solid is out into the liwuid, both of same density, will the solid float, sink or...?

Is it A, B or C ?

My Hypothesis: I guess that it will be at B.
My Reason: Since it is the same density, it will neither sink nor float, so it will remain in the middle.

According to research...to me, some of the information will be understood only if you went to the website...

...Methods depending on the free suspension of the solid in a liquid of the same density have been especially studied by Retgers and Gossner in view of their applicability to density determinations of crystals. Two typical forms are in use; in one a liquid is prepared in which the crystal freely swims, the density of the liquid being ascertained by the pycnometer or other methods; in the other a liquid of variable density, the so-called "diffusion column," is prepared, and observation is made of the level at which the particle comes to rest. The first type is in commonest use; since both necessitate the use of dense liquids, a summary of the media of most value, with their essential properties, will be given...

Taken from: http://www.1911encyclopedia.org/Density