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IB物理考试包括3个paper，paper1是选择题，paper2和paper3是简答题，对于很多学生来讲paper3是非常有难度的，为了帮助大家更好的应对这部分，今天留求艺留学为大家分享IB物理HL Paper3真题示例及备考技巧希望对大家有帮助。

IB物理HL Paper3真题示例

1.) A wheel of a mass of 0.27 kg that consists of a cylinder is mounted on the central shaft. The radius of the shaft is 1.4 cm and the cylinder, 4.2 cm. The shaft sits on two rails and is allowed to rotate and spin freely.

a.) The wheel is released from a stationary position and it rolls down the rail without slipping from Point A to Point B. The picture below shows the setup

The wheel leaves the rails at Point B and travels along a flat track from Point B to Point C. For a short while, a frictional force F exists towards point C between the edge of the wheel and the flat track

i.) The moment of Inertia of the wheel is 1.5 x 10-4 kgm2. Define inertia
Answer
Inertia is a property of matter that causes it to resist changes in velocity. It remains at the state of rest or in uniform motion in the same straight line unless acted upon by some external force.

ii.) While the wheel moves from Point A to B, the center of mass falls through a vertical distance of 0.43 m. Determine the translational speed of the wheel from Point A to Point after its displacement.
Answer
Kinetic Energy + Rotational KE = Gravitational Potential Energy
Therefore, ½ mv2 + ½ I x v2/r2 = mgh where r is the radius of the shaft
½ x 0.27 x v2 + ½ x 1.5 x 10-4 x v2/ (1.96 x 10-4) = 0.27 x 9.81 x 0.43
Rearranging and finding v, we have v = 1.48 m/s

iii.) Determine the angular velocity of the wheel at Point B
Answer
Angular velocity = velocity / radius (in meters)
Therefore, Angular velocity = 1.48 / 0.014 = 105.7 → 106 rad/s

iv.) Describe the effect of the frictional force on the linear speed of the wheel
Answer
Since the force is in the direction of the motion, the linear speed of the wheel increases.

v.) Describe the effect of the frictional force on the angular speed of the wheel
Answer
The angular speed decreases since the force gives rise to an opposing torque on the wheel.

2.) In an experiment, a student rolls paper into cylinders with the same diameter but different heights. The student then placed a fixed load on top of each of the cylinders one by one beginning with the cylinder with the shortest height. After, they recorded the height H of the first cylinder that was about to collapse. They then repeated the same process with different diameters of the cylinder. The graph below shows all the data recorded by the student. It is predicted that H (height) = cD2/3 where c is the constant

a.) Explain why the students data supports the theoretical prediction
Answer
According to the theoretical prediction, H3 is proportional to D2. When drawn in the graph, it is a straight line that goes through the origin – which is seen in the students graph above. Hence, it suggests that the data matches the prediction.

b.) Determine the constant c with an appropriate unit
Answer
c = gradient of the line
c = (46 – 12) / (16 – 4) = 34/12 = 2.83
c3 = 2.83 → c = 1.41
The unit for c is m1/3

c.) State one factor that would determine the constant c
Answer
The constant c could vary due to a number of factors. Some of them include the thickness of the paper, the weight of the fixed load and the number of times the paper is rolled into a cylinder (thickness of the cylinder itself).

IB物理HL Paper3备考技巧

1、paper3里的需要解释一个现象为什么会这样的问题，通常会考得最灵活。要是同学们遇到完全不知道如何下笔的这类题，可以先尽力找到相关的知识点或/和公式，把这个知识点先解释一遍，然后根据题意，把这个知识点带进入题的情况 里说一遍，为什么这个情况下会出现这个知识点描述的情况，就可以啦。

2、P3同样也是要多多刷题，Option的部分就不会有问题了。P3的Section A的Measurement and Uncertainties反而难度会比较大，因为考得很灵活。需要同学们熟练掌握如何 计算uncertainties，以及对题目里描述的实验的彻底理解，剩下的就是根据题意找出适用的相关知识点和公式了。

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