O-LevelPhysicsForces5054/22 · May/June 2024 · Q211 Marks

Fig. 2.1 shows a small swimming pool containing water. [Figure 2.1] The depth of water in the pool is 0.80 m. The density of water is 1000kg/m³.

(a)(i)Show that the mass of water in the pool is approximately 6700 kg.[2]
(a)(ii)Define 'pressure'.[1]
(a)(iii)Calculate the pressure on the base of the pool due to the water.[2]
(a)(iv)The water in the pool is initially at a temperature of 10°C. The temperature rises when 5.1 × 10º J of energy is transferred to the water. The specific heat capacity of water is 4200 J/(kg°C). Calculate the final temperature of the water.[3]
(b)(i)Explain, in terms of the movement of particles, how evaporation causes cooling.[2]
(b)(ii)Changes to factors in the environment of the swimming pool can cause an increase or decrease in the amount of evaporation from the surface of the water. State two changes to environmental factors that increase the amount of evaporation from the surface of the water. 1 2[1]

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Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

2(a)(i) (V =) length × breadth × height in any form
2(a)(i) 6.7(2) × 1000 clearly seen or 6720 (kg) seen
2(a)(ii) force per unit area
2(a)(iii) Either (P =) dgh in any form, e.g.1000 × 9.8 x 0.8 Or (area of base) 2.1 × 4.0 or 8.4 (m²)
2(a)(iii) 7800 (Pa)
2(a)(iv) (ΔT =) E/mc in any form
2(a)(iv) 18 (°C)
2(a)(iv) 28 (°C)
2(b)(i) fastest moving / more energetic particles escape
2(b)(i) leaving slowest / less energetic particles
2(b)(ii) ANY 2 from higher temperature / wind / low humidity

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