PAPER 2

©chcphysicspll Prepared by Mdm. Phang Li Lee

Example 1 (SPM 2005; Question 9)

A fisherman finds that his boat is at different levels in the sea and in the river although the boat carries the same load. The density of the sea water is 1025 kg m-3 and of river water is 1000 kg m-3. Figures 1.1 and 1.2 illustrate the situation of the boat in the sea and in the river.

Figure 1.1 Figure 1.2 Using Figures 1.1 and Figure 1.2, compare the levels of the boat and the volumes of water displaced by the boat. [2 marks]

SUGGESTED ANSWER: - The level of the boat submerged in Figure 1.1 is less

than that in Figure 1.2 (or vice versa)

The level of the boat submerged in Figure 1.2 is more than that in Figure 1.1

- The volume of sea water displaced in Figure 1.1 is lower than that in Figure 1.2 (or vice versa) -

M1

M1

Section B

PAPER 2

©chcphysicspll Prepared by Mdm. Phang Li Lee

Relating the mass of the boat with its load, the volume of water displaced and the density of the water, deduce a relevant physics concept. [3 marks]

SUGGESTED ANSWER:

- The mass of the boat with its load in both figures are the same

(Information of mass is given by the question: The boat carries the same load.) - The density of sea water is higher than that of river

water. (Information of DENSITY are given by the question: The density of the sea water is 1025 kg m-3 and of river water is 1000 kg m-3.)

M1

M1

PAPER 2

©chcphysicspll Prepared by Mdm. Phang Li Lee

Figure 1.1

(Sea) Figure 1.2

(River) The level of the boat submerged

The volume of water displaced

Mass of the boat with its load

Same Same Density of water

SUGGESTED ANSWER:

- When the density of water displaced increases, the volume of water displaced decreases.

M1

PAPER 2

©chcphysicspll Prepared by Mdm. Phang Li Lee

Example 2 (SPM 2006; Question 10) Diagram 2.1 and Diagram 2.2 show wire coils connected to the ammeters, switches and d.c. power supply. When the switch is on and iron filings of the same amount is spread out each of the cardboard surface, the pattern of the iron filings is formed as shown in the diagrams.

Diagram 2.1 Diagram 2.2 Using Diagrams 2.1 and Figure 2.2, compare the number of turns of the coils, the pattern of the iron filings and angle of deflection of the ammeter indicator. [3 marks]

SUGGESTED ANSWER: - The number of turns of the coils in Figure 2.2 is more

than that in Figure 2.1 (or vice versa) - The pattern of iron filings in Figure 2.2 is more than

that in Figure 2.1 (or vice versa) - The angle of deflection of the ammeter indicator in

Figure 2.2 is greater / more than that in Figure 2.1 (or vice versa)

M1

M1

M1

PAPER 2

©chcphysicspll Prepared by Mdm. Phang Li Lee

State the relationship between the strength of the magnetic field and (i) the pattern of the iron filings (ii) the number of turn of the coils [5 marks]

Figure 2.1 Figure 2.2

The number of turns of the coils The pattern of iron filings The angle of deflection of the ammeter indicator

The strength of magnetic field ? ?

SUGGESTED ANSWER: - When the strength of the magnetic field increases, the

pattern of iron filings increases. - When the number of turn of the coils increases, the

strength of the magnetic field increases.

M1

M1

PAPER 2

©chcphysicspll Prepared by Mdm. Phang Li Lee

Example 3 (SPM 2009; Question 9)

Diagram 3.1 shows the effect of pressure on a sandy beach when a man sits on a chair. Diagram 3.2 shows the same man sitting on the same chair after a piece of plank is placed under the chair.

Diagram 3.1 Diagram 3.2 Observe Diagram 3.1 and Diagram 3.2, compare the depth of sinking, the load and the area of contact with the sandy beach. [3 marks]

SUGGESTED ANSWER: - The depth of sinking in Diagram 3.1 is more than that

in Diagram 3.2 (or vice versa) - The load exerted in Diagram 3.1 and Diagram 3.2 are

the same - The area of contact in Diagram 3.1 is less than that in

Diagram 3.2 (or vice versa)

M1

M1

M1

PAPER 2

©chcphysicspll Prepared by Mdm. Phang Li Lee

Relate the depth of sinking with the pressure exerted by the chair to make a deduction on the relationship between the pressure and the area of contact in this situation. [2 marks]

Figure 3.1 Figure 3.2

The depth of sinking The load exerted Same Same The area of contact Pressure ? ?

SUGGESTED ANSWER: - When the pressure exerted by the chair increases, the

depth of sinking increases. - When the area of contact increases, the pressure

decreases.

M1

M1