PRESSURE PASCAL’S LAW

PRESSURE
PASCAL’S LAW
Lecture : Purwanti Widi H, M.Pd










The member of group:

Fetik Rahayu 09312241013
Tri Sulis Setyawati 09312241027
Muhammad Izzatul Faqih 09312244025
Endah Dani P 09312244034
Wihdah H. N 09312244050




Science Education Mathematic and Science faculty
Yogyakarta State University
2010


PASCAL’S LAW
Goal:
Observing changes in fluid pressure is applied to the closed direction.
B. Basic Theory
Pressure is an effect which occurs when a force is applied on a surface. Pressure is the amount of force acting on a unit area. The symbol of pressure is P. Law can be stated as follows pascal that pressure is held outside the liquid is in a closed room will be forwarded by the liquid is all directions with the same direction.
The formula mathematically:
P= F/A or P= (dF_n)/dA
Where:
P is the pressure,
F is the normal force.
Some of the tools that work under the law of Pascal is a hydraulic jack, hydraulic brakes and car lifter.
Huklum pascal : “ Tekana yang diberuiakan kepada zat cair akan diteruskan ke segala arah sama besar”(Giancoli, 2001)
Pancaran air akan keluar pada setiap lubang dan kekuatan pancaran tersebut sama rata ke segala arah.Hukum Pascal tidak hanya berlaku pada zat cair saja tetapi berlaku pula pada zat gas. Zat cair dan zat gas keduanya sering disebut dengan fluida.Alat-alat teknik yang bekerjanya berdasarkan hukum Pascal antara lain: dongkrak hidrolik, kempa/alat pengepres hidrolik, rem hidrolik, pompa hidrolik, alat pengangkat mobil di tempat-tempat cucian mobil atau di bengkel, dan berbagai alat yang lain. (http://mahasiswasibuk.co.cc/1_7_Pipa-U.html)
Ketika fluida berada dalam keadaan tenang, fluida memberikan gaya yang tegak lurus ke seluruh permukaan kontaknya. Ketika fluida memberikan gaya aksi terhadap permukaan, di mana arah gaya tidak tegak lurus, maka permukaan akan memberikan gaya reaksi yang arahnya juga tidak tegak lurus. Hal ini akan menyebabkan fluida mengalir. Tapi kenyataannya fluida tetap diam. Jadi kesimpulannya, pada fluida diam, arah gaya selalu tegak lurus permukaan wadah yang ditempatinya. Sifat penting lain dari fluida diam adalah fluida selalu memberikan tekanan ke semua arah.
Pengaruh kedalaman terhadap Tekanan
Dua sifat fluida statis (fluida diam), yakni memberikan tekanan ke segala arah dan gaya yang disebabkan oleh tekanan fluida selalu bekerja tegak lurus terhadap permukaan benda yang bersentuhan dengan fluida tersebut.
Keterangan : w adalah berat air, h = ketinggian kolom air dalam wadah yang berbentuk silinder, A = luas permukaan dan P adalah tekanan.

Massa kolom zat cair adalah :

Jika kita masukan ke dalam persamaan Tekanan, maka akan diperoleh :

Pa = tekanan atmosfir. Pada gambar di atas tidak digambarkan Pa, tapi dalam kenyataannya, bila wadah yang berisi air terbuka maka pada permukaan air bekerja juga tekanan atmosfir yang arahnya ke bawah. Tergantung permukaan wadah terbuka ke mana. Jika permukaan wadah terbuka ke atas seperti pada gambar di atas, maka arah tekanan atmosfir adalah ke bawah.
Berdasarkan persamaan di atas, tampak bahwa tekanan berbanding lurus dengan massa jenis dan kedalaman zat cair (percepatan gravitasi bernilai tetap). Jika kedalaman zat cair makin bertambah, maka tekanan juga makin besar. Ingat bahwa cairan hampir tidak termapatkan akibat adanya berat cairan di atasnya, sehingga massa jenis cairan bernilai konstan di setiap permukaan. Jika perbedaan ketinggian sangat besar, massa jenis sedikit berbeda. Tapi jika perbedaan ketinggian tidak terlalu besar, pada dasarnya massa jenis zat cair sama (atau perbedaanya sangat kecil sehingga diabaikan).
(http://www.gurumuda.com/tekanan-dalam-fluida)

C. Tools and Matterials
Three (3) balloons
Injections
Water
Bucket
D. Procedures
Prepare tools and materials that need do experiment.
Make a hole in balloon 1, three holes in balloon 2, five holes in balloon 3.
Dip the balloons into the water in the bucket.
Tide injections in the mouth of the balloons that has been hollowed.
Remove balloons from the water and hit with strong shot to give the piston in a high pressure and low pressure on the water.
Observe jets that happen in different pressure.
Repeat the experiment with more hollow than before experiment.




E. Data table
No. Number of hole (s) High pressure Low pressure
1. 1 Far Near
2. 3 Far (hole 1 > hole 2 > hole 3) Near (hole 1 > hole 2 > hole 3)
3. 5 Far (hole 1 > hole 2 > hole 3 > hole 4 > hole 5) Near (hole 1 > hole 2 > hole 3 > hole 4 > hole 5)

F. Data Analysis and Discussion
In this practice, we will analysis pressure with the topic Pascal’s Law. This practice have goal to observing changes in fluid pressure is applied to the closed direction. The method of this practice is prepare tools and materials that need do experiment. Make a hole in balloon 1, three holes in balloon 2, five holes in balloon 3. Dip the balloons into the water in the bucket. Tide injections in the mouth of the balloons that has been hollowed. Remove balloons from the water and hit with strong shot to give the piston in a high pressure and low pressure on the water. Observe jets that happen in different pressure. Repeat the experiment with more hollow than before experiment.

The practice of obtaining data that fall distance of water flow with a hole 1 which were treated with a large pressure fall distance of the water flow is also large when compared with providing treatment with low pressure.
For a given a 3-hole balloon was found that after being treated with great pressure, the hole a distance down the flow of water larger than the hole 2. And the second hole spacing falling stream of water larger than the hole 3. Similarly, if given the treatment by providing a small pressure results are also similar except that a different distance shower.
Based on experiments conducted that, the hole that is at least near the surface will have a tremendous pressure, while the holes in the surface of the liquid pressure is much smaller. It did not fit the theory because the balloon material is very flexible and giving the pressure from the side.

Picture a balloon:







a. Treatment with large pressure






b. Treatment with small pressure
For a given balloon 5 hole showed that after treated with great pressure, the hole a distance down the flow of water larger than the hole 2. And the second hole spacing falling stream of water larger than the hole 3. And the third hole distance falling stream of water larger than the hole 4. And the fourth hole distance falling stream of water larger than the hole 5. Similarly, if given the treatment by providing a small pressure results are also similar except that a different distance shower. From the experiments conducted showed that the most distant water flowing in the hole at the top due to tremendous pressure occurs in the top hole. This is because flexible balloon material and technical provision of the pressure from the side. This experiment does not fit with the theory.
Pascal law says that the pressure exerted on the liquid will be forwarded to all directions equally (Giancoli, 2001: 239). In theory, the most distant water flowing in the hole bottom (greatest depth). The pressure that is pushing the water to exit through the hole. Holes that are at the point farthest from the surface will have tremendous pressure. The gap between theory and experiment results is due to lab equipment that do not meet the conditions that cause the variable-variable dick neglected. In this experiment, the liquid space is a balloon that is flexible and has a bulging shape. Two of these properties is what causes the pressure received by each hole to be much different from one another so greatly affect the distance the water stream coming out of the hole. Compare distance jets of water coming out of the hole between the holes with a hole the other one should only be influenced by the location of the hole from the bottom of the container only, hole closest emission produces a rich bottom of the container will most distant.

Answer Questions
Describe what happen if balloon hit with high pressure and low pressure, compare it!
Answer : The experiment this time we do not distinguish between the pressure, because we did not include a balloon into the bucket containing water. At the time of balloon filled with water and punched the water gushing from a hole is made, the water gushing in every hole, made three number of holes, 1 hole, 3 hole and 5 hole. At first hole gushing water farther from the hole to 2, the 2nd hole farther from the hole to 3, the 3rd hole farther from the hole 4 and the 4th hole farther from the hole to 5.

Compare condition of water in balloon with one hole, three holes, and five holes !
Answer : State of water at one hole gushing water. State of water during the first three holes further than the second hole and second hole further than the third hole. State of water during the five holes on the first hole gushing water farther from the second hole, second hole gushing water farther than the third hole, third hole gushing water farther from the fourth hole and the fourth hole gushing water farther from the hole to five .

Conclude your observation !
Answer : Based on experiments conducted it can be concluded that the water can radiate in all directions, this is evidenced by the emission of water in all the holes that exist on the balloon not only shine on one hole.

F. Conclusion
Based on the experiments conducted it can be concluded that the water can radiate in all directions, this is evidenced by the emission of water in all the holes that exist on the balloon not only shine on one hole. Based on the results of an experiment that produces jets of water hole farthest away is the top hole. This experiment can not prove the truth of law as a tool used pascal ineligible because balloon bending and bulging, so that the given pressure distribution is uneven.

G. Reference
Giancoli. 2001. Fisika Dasar Jilid 1.Jakarta: Erlangga.
http://mahasiswasibuk.co.cc/1_7_Pipa-U.html)