# data[].attributes.body
We saw a video and the teacher ask to us:
"why the boats float?"
Following the formula do•Vo• ~g~ = df• Vf• ~g~ (where the gravity is rased because is equal) the density of the fluid is bigger than the total density and the volume of the fluid is lower than the volume of the object.

The boat floats because the formula is respected.

The bauancy(spinta di Archimede) can be:
bigger,lower or equal than the weight of the object.

Why the titanic sinks?
In addition due to the high velocity and storm, the titanic sank for the scarcity of materials used to build the hull.
Some metallurgists found that the quality of the rivets wasn't the same in all.

# data[].attributes.body
In that lesson the teacher introduced the archimedes' principle and we saw this videos.
Archimedes' principle:when a body is complitely or partially immersed in a fluid, the fluid exerts an upward force on the body equal to the weight of the fluid displaced by the body.

Watch:https://ed.ted.com/on/Ek8wIVVv
Think:(Explain in your own words how Archimedes solved the crown's problem.)
Archimede had to discover if the density of the king's crown corresponded to the one of the gold.

Given that the formula to calculate density is D=m/V (density=mass/volume) he had to find the mass and the volume, he already knew the mass but the problem was about its volume because it had a particular shape. One day , while he was having a bath, he noticed that when he immersed himself in the water it rose , so he find out that the volume of the displaced water corresponded to the volume of his body. Thanks to this discovery he understood that he had to immerse the crown in water and see how much displaced water there was so as to know its volume. Knowing the volume he managed to calculate the density of the crown and compare it to the one of the pure gold solving  king's problem.

Watch:https://www.youtube.com/watch?v=dMvfv3aDa0E&feature=youtu.be
In retail 3:18 of this second video Archimedes dips a "balance two arms" in water. The arm with coins is more lowered. Why?
The coins lie because they are made of gold and thanks to this experiment discovers that the crown is made of gold and silver, therefore, has a lower density and higher volume.

# data[].attributes.body
In that lesson we gave a mark from 0 (incorrect) to 2 (perfect) to the answers at the questions that every group had previously done for assignment.  We also self-evaluated in order to understand if we were aware of how well/bad we had worked. Our group failed in self-evaluation because we thought our answer were correct while they weren't. Thanks to it we reformulated the answers to make them clearer and more correct than they were before.

# data[].attributes.headline
HOMEWORK: EXPLAIN THE TWO FOLLOWING IMAGES 

# data[].attributes.subject
HOMEWORK: EXPLAIN THE TWO FOLLOWING IMAGES 

# data[].attributes.body
1st) In the first image the pressure increases depending on the depth it's applied (obviously the deeper it is the bigger it is). In this case this happens because there's more water following Stevin's law: P=p0+dgh

2nd) In the second image the height of the water is the same, so the pressure is the same, following the Stevin's law: P=p0+dgh. For this reason the water spread out at the same way despite of the size of the containers.

# data[].attributes.body
°HYDROSTATICS° (2nd part)
In that lesson we learnt what are Pascal principle and Stevin's law:

Pascal principle: any changed in the pressure applied to a complitely enclosed fluid is trasmitted undiminished to all parts of the fluid and the enclosing walls.

Stevin's law principle: the pressure at a point in a liquid in static equilibrium depends only on the depht at that point. P=P0+dgh

We also saw some videos to understand better what those principles really explain:
Pascal principle --> the fluid mechanics hydraulic lift experiment (https://youtu.be/XuLO_TuvB80?list=PL6mT5ziOF3j5DB1l18kc1l0cGAG28) and the beer's bottle experiment (https://youtu.be/lj3x2U4CaEs).
About the Stevin's Law we have to research the applications in everyday life. he most important demonstration of this law is the experiment of the communicating vessels --> https://youtu.be/7gm4_xtlmBg

# data[].attributes.headline
HOMEWORK: ANSWER THE FOLLOWING QUESTIONS (HYDROSTATICS 1st part)

# data[].attributes.subject
HOMEWORK: ANSWER THE FOLLOWING QUESTIONS (HYDROSTATICS 1st part)

# data[].attributes.body
1st) Why are snowshoes much more effective for walking on snow?
Snowshoes are much more effective for walking on snow because their sole is bigger than a normal one and so, double its area and presuming that the force applied does not change, the pressure becames half.

2nd) Why does a sharp knife cut better that a dull one?
A sharp knife cuts better than a dull one because its blade is by far thinner than the one of dull knife and, for this reason, the point of contact between the blade and what you have to cut is smaller. Undoubtedly, presuming that we apply the same force in both cases, using a sharp knife will result much easier due to the greater pressure we manage to exert thanks to the smaller surface of the point of contact.

3rd) Why is a karate chop much more effective than an open-handed slap?
A karate chop is much more effective than an open-handed slap because split in half the surface of the point of contact between the hand and what we hit we exert the double of the pressure.

These phenomenons happen due to the fact that pressure and area are inversely propotional following the formula: P=F/A.

# data[].attributes.body
MATERIAL USED (what you need to do it) :
- 2 balloons
-push pins (almost 30)

PROCEDURE (how to do it):
1st step: blow up both balloons. ;
2nd step: proceed placing just one push pin on a surface, then take the first balloon and put it on the top of the push pin and try pushing it down using a little force;
3rd step: repeat the procedure, using the second balloon and all the push pins.

OBSERVATIONS (what you can notice):
a. In the first case the balloon blows up.
b. In the second case the balloon doesn't blow up.

CONCLUSIONS (what you've learnt and how you explain how it works):
Aware of we can calculate pressure dividing the applied force for the area taken into consideration we can affirm that if the area increases, pressure decreases (given that they are indirectly proportional).
In balance, in the first case the balloon blows up because the pressure is bigger than in the second one, and, obviously, it's depends on the area.

ENJOY THE EXPERIMENT SHOWN IN THE VIDEO BELOW!

# data[].attributes.attachment_link.title
Balloon and pin - the balloon does not break - a physical experiment HD

# data[].attributes.attachment_link.description
Subscribe! http://www.youtube.com/subscription_center?add_user=igor30 The experiment was feasible in the home. Need balloon and pushpins. Put a few pins and then press it in a balloon. You'll see that the balloon does not burst. Surface of the balloon pressure is distributed evenly to all the pins, so the balloon does not break.

# data[].attributes.headline
KLIL-PHYSICS IN ENGLISH (THURSDAY 02/09/2017)

# data[].attributes.subject
KLIL-PHYSICS IN ENGLISH (THURSDAY 02/09/2017)

# data[].attributes.body
°HYDROSTATICS°

We were shown seven different hydrostatic’s experiments:

1st) PLASTICINE IN WATER:
If you put a ball-shaped piece of plasticine in a cup of water it will sink.
If you give it the shape of a boat it will float.

2nd) SYRINGES WITH AIR:
You have a syringe (which you can fill with whatever you want: such as water, oil or just air)and if you push the first you will notice that piston the other goes up.
(just like every plumming works like ! )

3rd) SYRINGES WITH COLOURED WATER:
You put a few drops of dye in a glass of water (so that you colour it) then you fill the syringes with it.
You will notice that if you move the syringes up and down the level of the water changes depending on how you move them.

4th) FISH IN THE BOTTLE:
You have a bottle of water and a plastic fish and if you squeeze the bottle the fish sinks as deep as the force you use .

5th) BOTTLE WITH TWO HOLES:
You have a bottle of water with two holes and the water comes out differently from the lowest to the highest. You will notice that the ranges increase with the distance from the hole to the free Surface.

6th) BOTTLE WITH ONE HOLE:
You have a bottle of water with one hole. If you put the cork the water stops from falling even if the level of the water is higher than the hole.

7th) SYRINGES WITH FIVE HOLES:
We had a syringe with water and if you push the piston the water comes out differently from the every hole.

# data[].attributes.body
HYDROSTATICS: the branch of fluid mechanics that studies fluids at rest-
FLUID: a substance that can flow(like liquid and aeriform substance). Fluids conform to the boundaries of the container in which they are placed.

DENSITY: the ratio of a given mass of the substance and its volume.
d=m/v
unit of measurement: kg/m^2
The higher is the temperature of a substance the smaller is its density because its volume increases with temperature.

PRESSURE: is the magnitude F of a force acting perpendicular dividing by the area S of  the Surface over which the force acts.
P=Fperp./S
IMPORTANT!!
pressure isn't a vector quantity but a scalar quantity.
Force and Area= directly proportional
Pressure and Area = inversely proportional
Pressure and Force = directly proportional

Finally the teacher asked us to answer to these questions:
1) Why are snowshoes much more effective for walking on snow?
2) Why does a sharp knife cut better than a dull knife?
3) Why is a karate chop much more effective than an open-handed slap?