contoh soal dan pembahasan thermodinamika

1. Suatu gas memiliki volume awal 2,0 m3 dipanaskan dengan kondisi isobaris hingga volume akhirnya menjadi 4,5 m3. Jika tekanan gas adalah 2 atm, tentukan usaha luar gas tersebut!

(1 atm = 1,01 x 105 Pa)

 Kunci : 5,05 x 105 joule

2. 1,5 m3 gas helium yang bersuhu 27oC dipanaskan secara isobarik sampai 87^oC. Jika tekanan gas helium 2 x 105 N/m2 , gas helium melakukan usaha luar sebesar….

A. 60 kJ

B. 120 kJ

C. 280 kJ

D. 480 kJ

E. 660 kJ

(Sumber Soal : UMPTN 1995)

Kunci : 60 kJ

3. 2000/693 mol gas helium pada suhu tetap 27oC mengalami perubahan volume dari 2,5 liter menjadi 5 liter. Jika R = 8,314 J/mol K dan ln 2 = 0,693 tentukan usaha yang dilakukan gas helium!

Kunci : 4988,4 joule

4. Mesin Carnot bekerja pada suhu tinggi 600 K, untuk menghasilkan kerja mekanik. Jika mesin menyerap kalor 600 J dengan suhu rendah 400 K, maka usaha yang dihasilkan adalah….

A. 120 J

B. 124 J

C. 135 J

D. 148 J

E. 200 J

(Sumber Soal : UN Fisika 2009 P04 No. 18)

Kunci : 200 J

5. Diagram P−V dari gas helium yang mengalami proses termodinamika ditunjukkan seperti gambar berikut!

Usaha yang dilakukan gas helium pada proses ABC sebesar….

A. 660 kJ

B. 400 kJ

C. 280 kJ

D. 120 kJ

E. 60 kJ

(Sumber Soal : UN Fisika 2010 P04 No. 17)

Kunci : 400kJ

6. Suatu mesin Carnot, jika reservoir panasnya bersuhu 400 K akan mempunyai efisiensi 40%. Jika reservoir panasnya bersuhu 640 K, efisiensinya…..%

A. 50,0

B. 52,5

C. 57,0

D. 62,5

E. 64,0

 (Sumber Soal : SPMB 2004)

Kunci : 62,5%

7. Perhatikan gambar berikut ini!

Jika kalor yang diserap reservoir suhu tinggi adalah 1200 joule, tentukan :

a) Efisiensi mesin Carnot

b) Usaha mesin Carnot

c) Perbandingan kalor yang dibuang di suhu rendah dengan usaha yang dilakukan mesin Carnot

d) Jenis proses ab, bc, cd dan da

kunci : 40%, 480 joule, 3 : 2

Soal No. 8

Suatu gas ideal mengalami proses siklus seperti pada gambar P − V di atas. Kerja yang dihasilkan pada proses siklus ini adalah….kilojoule.

A. 200

B. 400

C. 600

D. 800

E. 1000

Kunci : 400kJ

pembahasan 

      Pembahasan no 1

V2 = 4,5 m³  V1 = 2,0 m³

P = 2 atm = 2,02 x 10⁵ Pa

Isobaris → Tekanan Tetap

W = P (ΔV)

W = P(V2 − V1)

W = 2,02 x 10⁵ (4,5 − 2,0) =  5,05 x 10⁵ joule

      Pembahasan no 2

V₁ = 1,5 m³

T₁ = 27^oC = 300 K

T₂ = 87^oC = 360 K

P = 2 x 10⁵ N/m2

W = PΔV

Mencari V₂ :

V₂/T₂ = V₁/T₁

V₂ = ( V₁/T₁ ) x T₂ = ( 1,5/300 ) x 360 = 1,8 m³

W = PΔV = 2 x 10⁵(1,8 − 1,5) = 0,6 x 10⁵ = 60 x 10³ = 60 kJ

      Pembahasan no 3

n = 2000/693 mol

V₂ = 5 L

V₁ = 2,5 L

T = 27^oC = 300 K

Usaha yang dilakukan gas :

W = nRT ln (V₂ / V₁)

W = (2000/693 mol) ( 8,314 J/mol K)(300 K) ln ( 5 L / 2,5 L )

W = (2000/693) (8,314) (300) (0,693) = 4988,4 joule

      Pembahasan no 4

η = ( 1 − Tr / Tt ) x 100 %

Hilangkan saja 100% untuk memudahkan perhitungan :

η = ( 1 − 400/600) = 1/3

η = ( W / Q1 )

1/3 = W/600

W = 200 J

      Pembahasan no 5

W_AC = W_AB + W=

W_AC = 0 + (2 x 105)(3,5 − 1,5) = 4 x 10⁵ = 400 kJ

      Pembahasan no 6

Data pertama :

η = 40% = 4 / 10

Tt = 400 K

Cari terlebih dahulu suhu rendahnya (Tr) hilangkan 100 % untuk mempermudah perhitungan:

η = 1 − (Tr/Tt)

4 / 10 = 1 − (Tr/400)

(Tr/400) = 6 / 10

Tr = 240 K

Data kedua :

Tt = 640 K

Tr = 240 K (dari hasil perhitungan pertama)

η = ( 1 − Tr/Tt) x 100%

η = ( 1 − 240/640) x 100%

η = ( 5 / 8 ) x 100% = 62,5%

      Pembahasan no 7

a) Efisiensi mesin Carnot

Data :

Tt = 227_oC = 500 K

Tr = 27_oC = 300 K

η = ( 1 − Tr/Tt) x 100%

η = ( 1 − 300/500) x 100% = 40%

b) Usaha mesin Carnot

η = W/Q₁

4/10 = W/1200

W = 480 joule

c) Perbandingan kalor yang dibuang di suhu rendah dengan usaha yang dilakukan mesin Carnot

Q₂ = Q₁ − W = 1200 − 480 = 720 joule

Q₂ : W = 720 : 480 = 9 : 6 = 3 : 2

d) Jenis proses ab, bc, cd dan da

ab → pemuaian isotermis (volume gas bertambah, suhu gas tetap)

bc → pemuaian adiabatis (volume gas bertambah, suhu gas turun)

cd → pemampatan isotermal (volume gas berkurang, suhu gas tetap)

da → pemampatan adiabatis (volume gas berkurang, suhu gas naik)

      Pembahasan no 8

W = Usaha (kerja) = Luas kurva siklus = Luas bidang abcda

W = ab x bc

W = 2 x (2 x 105) = 400 kilojoule

a spceech contest text

Assalamualaikum Wr. Wb

Honorable adjudicators,

Dear brothers and sisters.

Ladies and gentlemen,

I would like to introduce myself. My name is Fika Maslakha. I am the student of Islamic Senior high school in Sidoarjo. I am pleased to have the opportunity to meet you all and I am hoping that with this activity everybody here could express all the best of them. In this great opportunity, allow me to deliver my speech with the title “Global Warming: The Cause, Effect and the solution.

Ladies and gentlemen,

Global warming is the increase in temperature of the earth’s atmosphere that is caused by the increase of particular gases especially carbon dioxide. What causes global warming? Many experts believe that our production of carbon dioxide and other greenhouse gases is heating the atmosphere, and this could be very dangerous for human life. Carbon dioxide and other air pollution that is collecting in the atmosphere like a thickening blanket, trapping the sun’s heat and causing the planet to warm up.

 So now, how can we as individuals do our part to help saveing the planet? The answer is simpler than you may think. You don’t have to go miles away from home to protest, or spend masses of money. If you try to follow the few simple steps that I shall now give you, you will have started to help this earth.

Firstly, plant a tree. This could be easier than it sounds. Join or help out a local wildlife group and ask to plant a tree. Trees, when fully grown, will help keeping the planet cooler. On the same point, you could protest against the demolition of the rainforests. This is the same principle, we need the trees to cool our planet and yet they are chopping them down to create roads or homes.

Something as simple as walking instead of taking car will help reduce pollution. As well as stopping pollution, you are giving yourself exercise, something important for our bodies. So the next time you get into your car, or your motorbike, think twice or more, do I have to make this journey by vehicle or can I walk?

If possible, buy your fruit and vegetables from local suppliers. And try to avoid imported goods. The more foreign food that we import the more pollution from airplanes and boats it will create.

Keeping to the speed limit can also help the environment. The more you speed the more petrol you are going to use, making the pollution higher. Also, SUV’s make about six times their own weight in CO2 each year. A small efficient diesel car covering the same distance not only uses much less fuel; it makes two thirds less.

Reduce, reuse and recycle. Only buy what you need; don’t stock the cupboards with things you may or may not use. Reuse whatever you can, like containers and paper, and recycle what you cannot reuse. It really is as simple as that.

Finally turning off unused sources of power such as televisions and air conditioner will help the environment, as well as save your money.

If everybody stuck to these rules, we would be doing a great thing by protecting the earth. So please take into consideration what I have said, and try to do your part. After all, it will be our next generation that will feel the effects.

Ladies and gentlemen

As we meet here today, the good news is that after too many years of inaction and denial, there is finally widespread recognition of the urgency of the challenge before us. We know what needs to be done. We know that our planet’s future depends on a global commitment to permanently reduce greenhouse gas pollution. We know that if we put the right rules and incentives in place, we will unleash the creative power of our best scientists, engineers, and entrepreneurs to build a better world. And so many nations have already taken the first steps on the journey towards that goal. Thank you very much,

Wassalamualaikum Wr. Wb

cara membuat complaint letter

Well,,,,,  Guys, I have studied about ‘ How to Write A Complaint  Letters’.

I will give you a little thing about complaint letter and I myself also give you an example about complaint letter………

Check it out  !!

There are five components that we can see in Letters of complaint. They are B, P, S, W, and C. Here is the detail:

1.       Background

2.       Problem-cause and effect

3.       Solution

4.       Warning (optional)

5.       Closing

      Background

In this section, the writer describes the situation he / she has ; e.g.

-      I am writing to inform you that the goods we ordered two days ago from your company have not been supplied correctly.

-      I would like to inform you of my dissatisfaction with the food and drinks at the “MITRA KELUARGA” restaurant on Wednesday, 12 February 2012 at 07.15 p.m.

-      I am one of your customers who inform you about my complaint.

-      Etc… (you can write it by your own statement)

      Problem

In this section, the writer may tell about the cause and effect to the matters which is faced by writer. Look at the following example of statements.

Cause :

-      On 12^nd February  2012 we placed an order with your firm for 100 electric vouchers for mobile phone. The consignment arrived yesterday but contained only 90 electric vouchers for mobile phone.

-      We have found 55 spelling in your book.

-      Firstly, I had difficulty in registering to attend the event. You set up an on-line registration facility, but I found the totally facility unworkable.

-      Etc…

Effect :

-      After spending several wasted hours trying to register in this way, the computer would not accept my application.

-      So, I feel annoyed with condition like this. I can’t be relaxed.

-      Etc…

      Solution

In this section, the writer suggests or gives the solution to what problem he / she gets ; e.g.

-      I am writing to ask you to please make up the shortfall immediately and to ensure that such errors do not happen again.

-      Please service your customer well.

-      Etc…..

      Warning

In this section, the writer may warn to the person or institution he/ she complains. This section is not always appeared on the complaint letter. It means that the writer may write it or not (optional) ; e.g.

-        Otherwise, we may have to look elsewhere for our supplies.

-        I’m afraid that if these conditions are not met, we may be forced to take legal action.

-        I will never buy it in your shop.

      Closing

In the last section, the writer consists of the writer sate thankfulness and he/she hope…e.g.

-        I look forward to receiving your explanation of these matters.

-        I look forward to receiving your payment.

-        Etc……….

well, this is the example........