AQA GCSE Science



213741022606000Liquid under pressure – Analysis SheetAimsSome swimmers diving to the bottom of a swimming pool realise that the water pressure seems to increase at greater depths. They decide to enlist the help of the local fire brigade to find out whether this is the case. MethodFive hoses of different lengths were sealed at one end, and a tap was fitted to the side of each hose at the sealed end, with the tap nozzle set at right angles to the length of the hose.The hoses were suspended vertically and filled with water.The tap on the shortest hose was opened fully and the furthest horizontal distance, d that the water jet reached was measured. The tap was opened on each hose in turn. d was measured in each case.The hoses were then re-filled with water and the procedure repeated twice.The temperature of the water was taken to check that it was the same each time.ResultsHose length (m)d (cm)d (cm)d (cm)Mean d (cm)0000011214122222524337383844749485626260QuestionsComplete the table of results and calculate the mean values of d.Draw a line graph of mean distance (y-axis) against hose length (x-axis).What is the relationship between the hose length and the mean distance?If the hose length is an indication of the depth of water, what does the distance represent?To make it a fair test certain variables must stay the same. These are called control variables. The internal diameter of the hose is one control variable. State the control variable given in the method.Why were you able to draw a line graph of the results?There were small differences in the distance measured for each hose length. Suggest possible sources of error.What is the initial angle of the water as it flows, why is this? -19138656125000Teacher Answers / IssuesStudents analyse a fictional investigation of how the pressure in a liquid varies with depth. Students are often familiar with increase in water pressure with depth. They may not realise the two variables are directly proportional to one another.Some support may be needed to calculate the mean values (to the nearest 0.1 cm).Some support may be needed to draw the line graph.Answers to questionsCorrect calculation to nearest 0.1 cm (12.7 cm, 23.7 cm, 37.7 cm, 48.0 cm, 61.3 cm)Correct straight-line graph. Students should have drawn a line of best fit through the origin.Hose length is directly proportional to mean distance, or as the hose length gets longer the distance increases.The distance is an indication of the water pressure.Temperature of the water.The variable(s) were continuous.Any sensible answer: the hose not filled completely to the top; incorrect measurement of distance; difficulty finding end of water jet; tap opened at different speeds.90 degrees as the pressure acts on the sides equally in all directions and at 90 degrees. Then the weight pulls it downwards to form a parabolic path. ................
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