IB物理答案包括3个paper，paper1是选择题，paper2和paper3是简答题，其中不管是SL还是HL，Paper2都是占分数比例最大的，所以大家一定要重视这部分答案，今天考而思惟世为大家总结了IB物理HL Paper2真题示例及备考技巧，希望对大家有帮助。

IB物理HL Paper2真题示例

1.) The air in a kitchen has a pressure of 1.20 x 105 Pa and a temperature of 23 C. There is a refrigerator inside the kitchen with an internal volume of 0.38 m3.

a.) When the refrigerator door is open, the temperature and pressure of the air inside the kitchen and inside the refrigerator are the same. Calculate the number of air molecules in the refrigerator.

Answer
PV = nRT
N = PV / RT
N = (1.20 x 105 x 0.38) / ((273 + 23 ) x 8.314 = 18.529 = 18.5 mol
Number of molecules = 18.5 x 6.023 x 1023 = 1.1 x 1025

b.) When the refrigerator door is closed, the temperature inside cools down to 4 C with the same amount of air molecules.

i.) Determine the pressure of the air inside the refrigerator round to 3 significant figures

Answer
P1T1 = P2T2
1.2 x 105 x (273+23) = P2 x (273+4)
P2 = (1.20 x 105 x (273+23)) / (273+4)
P2 = 128231.0469 → (1.28 x 105 Pa)

ii.) The area of the door of the refrigerator is 0.75 m2. Determine the minimum force needed to open the refrigerator door.

Answer
Force = Difference in pressure x Area
Force = (128231 – 120000) x 0.75 = 6173.25 = 6.17 kN

2.) A closed box has a fixed volume of 0.21m3 and contains 4 mol of ideal monatomic gas. The temperature of the gas is 294 K.

i.) Calculate the pressure of the gas
Answer
PV = nRT
P = nRT / V
P = (4 x 8.3145 x 294) / 0.21 = 46561.2 Pa = 46.5 kPa

b.) When the gas is supplied with 0.81 kJ of energy, the temperature of the gas increases by 25 K. The specific heat capacity of the gas is 3.1 kJ / kgK

i.) Calculate the mass of the gas in kg

Answer
Q = mcΔT
M = Q / cΔT
M = 0.81 / (3.1 x 25) = 0.0104516 kg = 0.0105 kg

ii.) Determine the total kinetic energy of the gas particles in kJ

Answer
Average kinetic energy = 3/2 kB T
Avg KE = 3/2 (1.38 x 10-23) x 319 = 6.6033 x 10-21
Number of molecules = 4 x 6.023 x 1023 = 2.4092×1024
Total kinetic energy = 6.6033 x 10-21 x 2.4092×1024 = 15908.67036 J = 16 kJ

IB物理HL Paper2备考技巧

P2其实是所有paper里最难的，因为考得特别灵活，运算也多，通常会用到several steps和一个以上的公式。

P2考验同学们对知识点掌握的灵活度和熟练度，同时还有许多要用到Common Sense的地方，虽然说很多时候考完P1已经没有了。

P2需要同学们对每一个知识点透彻的理解，所以在学新知识点的时候一定不要学得似懂非懂，必须全部理解才行。

同样地，P2也可以用多刷题来解决，不过可以刷题的时候根据topic来给不同类型的题分类，比如Wave这个topic里WaveInterference会考的题有哪些类型，Simple Harmonic Motion会考的又有哪些类型，最后会发现IB很多题本质上都相似，万变不离其宗。

掌握了一类题的解决方法，不管它怎么变形，核心都是一样的，这样答案遇到什么题都不怕啦。记得一个大题的每道小题之间是相互关联的，要是有一个小题不知道怎么做，可以联系其他小题看能不能得到什么信息。

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