Page 37 - Pra U STPM 2021 Penggal 1 - Physics

Physics Term 1 STPM STPM Model Paper (960/2)
(iv) Estimate the energy dissipated from the wire in the loading and unloading process.
[3 marks]
Anggarkan tenaga yang terlesap daripada dawai semasa daya ditambahkan dan daya
dikurangkan. [3 markah]

20. (a) (i) Write an equation to represent the first law of thermodynamics. Explain clearly the
terms in the equation. [2 marks]
Tuliskan persamaan yang mewakili hukum termodinamik pertama. Jelaskan sebutan-sebutan dalam
persamaan. [2 markah]
(ii) Use the first law of thermodynamics to explain that in an isothermal expansion,
although heat is supplied to the gas, the temperature of the gas remains unchanged.
What happens to the heat supplied? [2 marks]
Gunakan hukum termodinamik pertama untuk menjelaskan bahawa dalam pengembangan isotermal,
walaupun haba dibekalkan kepada gas, suhu gas kekal tidak berubah. [2 markah]

(b) An ideal gas has a volume of V when its temperature is T and pressure is p . The gas
0 0 0
undergoes the following processes:
Pada suhu T dan tekanan p , isi padu suatu gas unggul ialah V . Gas itu melakukan proses berikut:
0 0 0
I: The pressure of the gas is increased to three times its initial pressure at constant volume.
I: Tekanan gas ditambahkan sehingga tiga kali tekanan asal pada isi padu malar.
II: The temperature of the gas is then reduced back to T at constant pressure.
0
II: Suhu gas kemudian dikurangkan sehingga T pada tekanan malar.
0
III: The gas expands isothermally until its volume is V and its pressure is p .
0
0
III: Gas itu mengembang secara isotermal sehingga isi padunya V , dan tekanannya p .
0
0
Determine in terms of p , V and T ,
0
0
0
Tentukan dalam sebutan p , V dan T ,
0
0
0
(i) the temperature of the gas after process I, [2 marks]
suhu gas selepas proses I, [2 markah]
(ii) the volume of the gas after process II, and [2 marks]
isi padu gas selepas proses II dan [2 markah]
(iii) the work done by the gas in the complete cycle. [4 marks]
kerja yang dilakukan oleh gas itu dalam satu kitar yang lengkap. [4 markah]
(c) Draw a p-V graph to illustrate the processes I, II and III. [3 marks]
Lukiskan graf p-V untuk menggambarkan proses-proses I, II dan III. [3 markah]
ANSWERS

PAPER 1 (b) (i) 45 o
2
2
Section A (ii) H = v sin 45° = 3.00 m
1. A 2. B 3. C 4. D 5. C 2g
6. D 7. A 8. D 9. D 10. B Or maximum R = v 2 = 2(6.0) m
11. A 12. B 13. B 14. C 15. C g
v = 10.8 m s -1
Section B 17. (a) (i) Ideal gas: Gas that obeys the ideal
v sin 45°
2
2
16. (a) H = gas equation pV = nRT for all
2g
temperatures and pressures.
2
R = 2v sin45° cos45° (ii) State of a gas is determine by its
g temperature, pressure and volume.
H 1 1
= tan 45° =
R 4 4
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MODEL PAPER PHY T1.indd 327 4/9/18 8:32 AM