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According to Archimede's principle, which states that an object partially immersed in a fluid is buoyed up by a force equal or bigger than the weight of the fluid displaced by the object, ships can float only if their weight is the same as the weight of water displaced, or even bigger.

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Considering that the density of pure gold (which coins are made of) is major than the density of silver, the arm with coins is more lowered than the one with the crown. That's because coins have a major density and, according to Archimede's principle, they sinks more.

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The rivets that were used in the forward hull where not made of the highest quality iron and where not uniformly inserted. For this reason the impact with which the boat hit the iceberg popped heads off of rivets opening gashes in the hull.

We know that Titanic had been built with 16 compartments, separated by bulkheads below the waterline. The bulkheads were sealed to keep the ship afloat even if all 4 forward compartments were flooded. Unfortunately the additional compartments flooded and the extra weight pulled Titanic low into the water.

As the rear of the ship rose out of the water, the hull broke and Titanic tore into 2 pieces. The forward section broke away and fell to the bottino of the Atlantic. The rear section continued to float upward toward the vertical before also plunging to the bottom of the ocean.

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How Archimedes solved the crown's  problem?

Archimede had to check if a goldsmith had cheated on the king by putting some silver in his crown, which was meant to be of pure gold, in order to take some gold for himself. He knew that silver was less dense than gold so, if the crown was made only of pure gold, it would have been more dense. He decided the compare the crown and some gold coins: considering that density formula is d=m/V, he had to find the volume of the gold coins and the crown. So, knowing that a crown can't be measured in a normal way he put it in water and observed how much water was displaced, because the volume of water spilled is equal to the volume of the immersed object. So in this way he could calculate the density of both objects and then he discovered that the crown wasn't made of pure gold because it was less dense than the gold coins.

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This is "FINDER 06 -STEVIN LAW" by Ardea elearning on Vimeo, the home for high quality videos and the people who love them.

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Pascal's law states that the pressure applied at one point of the liquid is transmitted equally in all direction. This principal is applied in hydraulic lift, for lifting heavy objects.

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PASCAL'S BARREL TRUE STORY
Pascal's barrel is the name of the pascal's experiment that he did to impress his friends. In the experiment pascal inserted a 10 meter long vertical tube in a barrel full of water. When the water was poured into the vertical tube, Pascal found that the increase in hydrostatic pressure causes the barrel to burst or break.
💣💣💣

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We know that in both containers the atmospheric pressure, the density and the gravity constant are the same. But, we can notice that they have also the same height, so their pressure is the same and it is the reason why the water spreads in the same way.

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First, the picture demonstrates the value of the pressure: in fact, the arrows represent the different pressures exerted. Thanks to them, we can see that the more the man goes down, the more the pressure increases. It depends on the formula P= Po + dgh, where Po, d and g are constant, while h, the height of the water, changes: if it increases, the pressure increases too.

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The water tower

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•Communicant Vessels: they are a set of containers containing a homogeneous fluid: when the liquid settles, it balances out to the same level in all of the containers regardless of the shape and volume of the containers. If additional liquid is added to one vessel, the liquid will again find a new equal level in all the connected vessels.

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2)STEVIN'S LAW

Stevin's Law states that the pressure at a point in a liquid in static equilibrium depends only on the depth at that point.

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Today we had a lesson about 2 different types of pressures.
1)PASCAL'S PRINCIPLE
Pascal's Principle states that any change in the pressure that is applied to a completely enclosed liquid is transmitted undiminished to all parts of the fluid and the enclosing walls.
EXAMPLE: If we fill a syringe that has holes with water and then we push the piston, we can notice that the water comes out from all the holes with the same speed perpendicularly to the surface of the container. This example reminds us of the seventh experiment we did the first lesson.
An application of the Pascal's Principle in everyday life is the hydraulic press. This reminds us of the second experiment we did the first time.

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Today with our group we did the self evaluation. We gave a mark to our and our friends previous experiments. The marks went from 0 to 2.

0 means that the answer was incorrect;

0,5 it is correct but we can do it better;

1 it's correct;

1,5 it is correct but something is missing;

2 the answer is perfect.

We have given high marks but some answers were incorrect so our self evaluation amounted to 0 points. 👎🏻👎🏻👎🏻

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Today we did an experiment. We used a carton of milk, some flour and a ruler to measure the area of the carton. We really enjoyed it ✌🏻.
The measures: A 7,2 cm. B 6,8 cm. C 19,7 cm
The weight: 1,7 kg
F= 1,7x9,81=16,68 N
1) CxA= 19,7x7,2= 141,8 cm^2
P= 16,68/0,01418= 1176 Pa
2) BxC= 6,9x19,7= 135,9 cm^2
P= 16,68/0,001359= 1227 Pa
3) AxB= 7,2x6,9= 49,7 cm^2
P=16,68/0,00497= 3356 Pa

What do you notice?
We know that for a given Force ( the weight of the milk's carton), Pressure and Area are inversely proportional. So we see that in case 1 we have the largest area and so the pressure is minor. In fact when we put the carton on the flour we notice that the hole that the carton creates is less evident. While in case 3 we have the smallesta  area and so the pressure is major. For this reason the hole in the flour is more evident.

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Our homework today is to find something about the experiment of the balloon and the pushpins. It can appear very easy but a lot of people don't know the reason why the balloon doesn't pop. In this experiment we have to inflate a balloon, next take a pushpin and place it on the table. Then we have to take the balloon and see what happens when we push it on the pins. As expected it pops. Later we have to take a lot of pushpins and position them near each other on the table, then try doing the same thing again. This time we can push it on the pins and it doesn't burst. This happens because the pressure is distributed over lots of pushpins and the amount of pressure on each pins is too small to burst the balloon.

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Kids Science Experiment Balloon Powered Car

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Kids Science: Balloon That Doesn't Pop With Pins

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Easy science experiment for children. We are popping balloons with Max today. It is simple with just one pin, but when the number of pins increases, the balloon doesn't pop (unless I push it really hard)

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1) Why snowshoes are much more effective for walking in snow?
We know that for a given Force, in this case my weight, Pressure and Area are inversely proportional. The snowshoe has a surface area larger than that of a normal shoe, so the pressure into the snow is lower and our feet don't sink.

2) Why does a sharp knife cut better than a full knife?
For a given Force, in this case the force that my arm exerts, if I diminish the Area, the Pressure will increase. We can notice that the sharp knife has a smaller area of contact with the surface than the dull knife, so the sharp knife will exert a major pressure on the surface than the second one. In conclusion, if you have to use a dull knife, you have to exert much more force in order to generate enough pressure to cut.

3) Why a karate chop is much more effective than an open-handed slap?
We know that for a given Force, in this case the force that my arm exerts, Pressure and Area are inversely proportional. With an open-handed slap, the area of force exertion is large and so the pressure is relatively small. While, with a karate chop, this force is exerted on a minimum area, so the pressure will be the maximum. It is the reason why a karate chop is more effective than a open-handed slap!

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5- BOTTLE WITH TWO HOLES (without cork)

In this experiment we see that the water comes out in two different ways from the holes. In the highest one the water goes out further than the lowest one.

6- BOTTLE WITH ONE HOLE (with cork)

In this experiment we notice that when the teacher puts the cork the water stops even if the water is higher than the hole, while when she removes the cork it comes out.

7-SYRINGE WITH FIVE HOLES

In this experiment the teacher uses a syringe with five holes, four of which are made by herself. We notice that if there's water in the syringe and we push the piston, the water comes out from the holes in 5 different ways.

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Today our teacher showed us seven physics' experiments.

1- PLASTICINE IN H2O

In this experiment we have two balls of plasticine that have the same weight. We notice that if we put one of the balls in the water, it sinks but if we change the shape of the other ball into a sort of boat, it floats.

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3- SYRINGES WITH COLOURED H2O💉

In this experiment we notice that if we move the syringes the coloured water inside them goes up and down and stops at a certain point.

4- FISH IN THE BOTTLE (with cork) 💧🐠

In this experiment we have a water full of water with a fish of plastic inside it. We see that if we push the bottle the fish sinks and if we squeeze it several times the fish goes up and down.

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WHAT IS A FLUID?

A fluid is a substance that can flow. Liquids (ex.water) and aeriform  substances (ex.smoke) are fluids.
They don't have their own shape but they conform to the boundaries of the container in which they are placed.

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2- SYRINGES WITH AIR

In this experiment we use two syringes linked with a small tube. If we push down one of the syringes' pistons the other one rises.

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The pressure is the ratio of a force (F) acting perpendicular to a surface and the area (S) of the surface over which the force acts.
P= F (perpendicular) / S
Their unit of measurement in the SI is N/m^2=Pa (pascal).

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Each substance has its own density at a given temperature (fixed number). The density is the ratio of a given mass of the substance and its volume:
density=mass/volume = m/V
Their unit of measurement is kg/m^3

+ temperature ----> - density
Why? Because the volume of the substance increases with temperature.

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!!! Pressure is not a vector quantity but a scalar quantity !!!

- For a given Pressure, Force and Area are directly proportional .
P(10)= F/A= 100/10 = 200/20
- For a given Force, Pressure and Area are inversely proportional.
F(10)= PxA= 5x2 = 10x1
- For a given Area, Pressure and Force are directly proportional.
A(10)= F/P = 20/2 = 40/4