Spm Tips: Physics Paper 2

Discuss your physics questions online at www.physics4spm.com EXAMPLE 1

Diagram below shows a model of a school bus. Rajah d bawah menunjukkan model sebuah bas sekolah.

Explain the modification to the bus to help to improve the safety of the passengers and will be more comfortable. Emphasise your explanation in the following aspects: (i) (ii)

the shape of the bus body safety features of the bus

Terangkan pengubahsuaian pada bus yang boleh meningkatkan keselamatan dan keselesaan penumpang. Dalam penerangan anda berikan penekanan bagi aspek-aspek berikut: (i) (ii)

bentuk badan bas ciri-ciri keselamatan dalam bas

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Discuss your physics questions online at www.physics4spm.com SUGGESTED SOLUTIONS

Modifications Reinforced passenger compartment (1 mark) Crumple zones These are specific points at the front and back portion of the car that are made to crumple progressively ( 1 mark ) Safety belt ( 1 mark ) Airbag ( 1 mark ) Narrower at the front shape ( 1 mark )

1. 2. 3.

Explanation The passenger should remain intact during a collision. It is made of high tensile strength steel that is able to withstand large forces (1 mark) Lengthen the time of collision, hence reduces the impulsive force on the bus. ( 1 mark )

Prevent passenger from jerking forward when the bus stop suddenly ( 1mark ) Lengthen the time of collision ( 1 mark ) To decrease air friction ( 1 mark )

Present the answers in table form Each fact must be followed by an explanation/reason Give short and accurate answer

1 mark is given for one modification and 1 mark is given for explanation. You can write more than that. Marks are not deducted for incorrect answers. Make sure that your answers are logic and acceptable by common sense. The examiners will not judge your grammar and linguistic arts; they will judge the facts only.

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Discuss your physics questions online at www.physics4spm.com EXAMPLE 2 Diagram below shows a hot air balloon carries up the loads at a certain height in the morning and diagram 10.2 shows the same hot air balloon carry up the loads at a certain height in the afternoon. This hot air balloon used helium gas at the same temperature in both situations. Rajah di bawah menunjukkan suatu belon udara panas mengangkat beban ke atas suatu ketinggian tertentu di waktu pagi dan Rajah 10.2 menunjukkan belon udara yang sama mengangkat beban ke atas suatu ketinggian yang tertentu pada waktu petang. Belon udara panas ini menggunakan gas helium pada suhu yang sama dalam kedua-dua situasi. In the morning (Waktu pagi) petang)

In the afternoon (Waktu

Number of load(bilangan beban)

h

h

Diagram A

Diagram B

Ground

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Discuss your physics questions online at www.physics4spm.com a. ( i ) What is meant by density? Apakah yang dimaksudkan dengan ketumpatan?

[1 mark]

( ii ) Using diagrams 9.1 and 9.2, compare the density of the air, the load that can be carry up by the hot air balloon and the height of the hot air balloon from the ground. Relate the buoyant force with the density of the air to make a deduction regarding the relationship between the density of the air and the weight of the load carry up by the hot air balloon. Menggunakan Rajah 9.1 dan 9.2, bandingkan ketumpatan udara, beban yang boleh diangkat ke atas oleh belon udara panas dan ketinggian belon udara panas dari tanah. Hubungkaitkan daya apungan dengan ketumpatan udara untuk membuat kesimpulan hubungan di antara ketumpatan udara dan berat beban yang diangkat ke atas oleh belon udara panas tersebut. [5 marks] b. Why does an iron nail sink in water but a cargo ship with a huge mass floats? Mengapa paku besi tenggelam di dalam air tetapi kapal kargo yang berjisim besar terapung? [4 marks]

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Discuss your physics questions online at www.physics4spm.com SUGGESTED SOLUTIONS (a) (i)

Density is ρ = m/V (this answer is incorrect) WHAT IS ρ? WHAT IS m? WHAT IS V? -

you must define the meaning of each symbol in the formula ρ = density m = mass V = volume

OR Present the answer in sentence and insert the formula as well ; -

Density is distribution of mass per unit volume of a substance ( 1 mark is given )

-

ρ = m/V , where ρ = density, m= mass and V = volume

(ii)

1

2

“Using diagrams 9.1 and 9.2 compare the density of the air, the load 3

that can be carrying up by the hot air balloon and the height of the hot air balloon from the ground. Relate the buoyant force with the density of the air to make a deduction regarding the relationship between the density of the air and the weights of the load carry up by the hot air balloon.” Step 1: Read the question and observe the diagrams carefully Step 2: What is required by the question? -

You are asked to compare 3 physics’ quantities, density, load and height. How to compare? You MUST use the sentences such as “A is bigger than B OR B is smaller than A”, “X is taller than Y OR Y is shorter than X” and etc. Therefore, your answers MUST be presented as ;

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Discuss your physics questions online at www.physics4spm.com “Density of air in Diagram A is greater than density of air in Diagram B” OR “Density if air in Diagram B is smaller than density of air in Diagram A” “The number of load in Diagram A is greater than in B” OR vice versa “The height of the balloons in both Diagram A and Diagram B are equal”

HOW TO RELATE? LOOK AT THE EXAMPLE BELOW: x 10 20 30 40 50 60

y 20 30 40 50 60 70

“ As x increases, y increases” x 10 20 30 40 50 60

y 70 60 50 40 30 20

“As y increases, x decreases” So, relationship is statement that describe the interaction between two variables. “Buoyant force increases as density of air increases” “Weight of load carries up increases as density of air increases” (b) Compare the correct density 1 Density of the iron nail is higher than the density of water// Average density of the cargo ship is lower than the density of water State the volume of water displaced 2 Volume/ weight of water displaced by the iron nail is smaller State the correct relation 3 For the cargo ship, the buoyant force is equal to its weight . 4 For iron nail , its buoyant force is smaller than the weight

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