A toy rocket is made from a 1.5 litre plastic bottle with fins attached for stability.
The bottle initially contains 0.30 litres of water, leaving 1.2 litres of trapped air at a temperature of 17°C.
A pump is used to increase the pressure of the air within the plastic bottle to 2.4 × 105 Pa at the start of lift-off.
Fig. 1.1 shows the rocket at the start of lift-off.
1 litre = 10–3m3
Fig. 1.1
amount of air = ................................. mol [2]
The temperature of this air remains constant.
Calculate the final pressure of the trapped air just before all the water has been released.
mass of empty bottle and fins = 0.050 kg
area of cross-section of hole = 1.1 × 10–4 m2
initial pressure of trapped air = 2.4 × 105 Pa
atmospheric pressure = 1.0 × 105 Pa
density of water = 1.0 × 103 kgm–3
initial acceleration = ................................... ms–2 [3]
[3]
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