A-level物理Structured question的答題套路

10月考試馬上就來了！最可怕的是，物理學科還要用英語答題，寫原因?qū)懲普搶懡Y(jié)果...很多學生大聲哭喊：“我的物理半壁江山要完了~救命啊”！

不要急，不要慌，馬上就來幫大家解決難題。

一般國內(nèi)學生計算能力，用公式水平，那是棒棒噠。但是呢，一遇到用英語表達的題目，那就秀才遇到兵了。

其實呢，物理中的英語表述題目也是有路可尋的。

看下面的例子：

例題一??(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)

■ 這屬于第一種類型：應用類，也被稱之為一一對應類。

就是把已知的物理原理定律等理清楚，然后看圖思考，把題目中的物理量與定律中的物理量一一對應。

先回顧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.

再回顧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.

例題二??(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)

■ 這屬于第二種類型：想象力的問題。

這個方面的考察那可是每年必備啊。想象力，太重要了，因為如果沒有想象力，科學就沒有進步，同樣，它也是科研探索必備素質(zhì)。答題的時候，每個人的想象力不同，所以答案五花八門。

但是，如何讓自己的答案既有想象力又能拿高分呢。親們別慌，回顧所學后進行正向或者逆向推理，大膽一些，答案不會太大問題的啦。

先回顧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

■ 這屬于第三種類型：比較題——比較兩種影響因素，或者兩種結(jié)論。

這種類型的題目看上去難度很大。可是只要我們回顧分析再加上想象和推理，就一定能戰(zhàn)勝它。

例題三?（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.

回顧：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.