A-level物理Structured question的答题套路

10月考试马上就来了！最可怕的是，物理学科还要用英语答题，写原因写推论写结果...很多学生大声哭喊：“我的物理半壁江山要完了~救命啊”！

不要急，不要慌，马上就来帮大家解决难题。

一般国内学生计算能力，用公式水平，那是棒棒哒。但是呢，一遇到用英语表达的题目，那就秀才遇到兵了。

其实呢，物理中的英语表述题目也是有路可寻的。

看下面的例子：

例题一  (edexcel-2010-Jun-question20)

The photograph shows a toy car driven by air from a deflating balloon.

When the air in the inflated balloon is released, the car starts to move forwards.

(a) Use Newton’s first and third laws of motion to explain why the air coming out of the

balloon causes this.(3)

■ 这属于第一种类型：应用类，也被称之为一一对应类。

就是把已知的物理原理定律等理清楚，然后看图思考，把题目中的物理量与定律中的物理量一一对应。

先回顾N3: the action force and the reaction force are equal in magnitude and opposite in direction,same type.

So the answer is：

The force on air by balloon and the force on balloon by air are equal in magnitude and opposite in direction,same type.

再回顾N1: the object will stay at rest or constant velocity unless resultant force on it.

So the answer is added：

The forward force on balloon is greater than drag force or air resistance, so there is a resultant force. By N1, the car moves from rest.

例题二  (edexcel-2017-Jan-question12)

Some paint manufacturers use pencils to test the hardness of paints using the equipment shown..

A pencil of known hardness is placed into a pencil tester and the tester is pushed across a surface coated in the paint under test.

This is repeated using pencils of increasing hardness until the paint becomes scratched.

(ii) Suggest two reasons why this method may not produce reliable results.(2)

■ 这属于第二种类型：想象力的问题。

这个方面的考察那可是每年必备啊。想象力，太重要了，因为如果没有想象力，科学就没有进步，同样，它也是科研探索必备素质。答题的时候，每个人的想象力不同，所以答案五花八门。

但是，如何让自己的答案既有想象力又能拿高分呢。亲们别慌，回顾所学后进行正向或者逆向推理，大胆一些，答案不会太大问题的啦。

先回顾Hard is the resistance for denting or scratching ,for example : diamond is hard.the instruments in the question is pencil, tester and paint, we use hands to do it.

So the answer is

For pencil：

Maybe pencils all have different cross- p area,sharpness and direction of motion.

For  tester：

testers all have different speed

For hand：

all hand exerts different force

For paint：

the paint are different thickness and not evenly on the table

■ 这属于第三种类型：比较题——比较两种影响因素，或者两种结论。

这种类型的题目看上去难度很大。可是只要我们回顾分析再加上想象和推理，就一定能战胜它。

例题三 （2019-Edexcel-Jan-Q11）

A student searched on the internet to find the reason why old eggs float.

Statement 1 old eggs float because as the egg ages it starts to decompose,as it decomposes gases are produced that escape through the eggshell.

Statement 2 as the egg ages air enters the egg through the eggshell and increases the size of the air cell,the larger air cell acts as a floatation device and hence old eggs float.

Assess which of these two statements is correct.

回顾：在水中，if weight>upthrust 就下沉，if upthrust>weight 就上升。

The Answer is :

statement 1 is correct.

Air escapes→density of eggs decreases→weight (mg) decreases,

Upthrust = ρgV constant

When resultant force  ρgV-mg>0 , By N1 the egg starts moving upwards

Statement 2 is wrong,weight increases, resultant force is downward, accelerate downwards.