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Physics Practical Determine acceleration of free fall using spiral spring • Position of hanger without mass must be larger than position of hanger with mass (base on diagram) • E = difference between the 2 readings • *Must convert to mm correctly • Difference between • T calculated correctly first and second (i.e. average / 20) & timing cannot be • Average • T given to 3 sf  Interval of 50 g more than 1 s.  calculated  correctly and • T2 calculated given to 2 dp correctly & T2 given  to 2 dp  Graph Plotting A – Axis labelled correctly with quantity / unit P – Points plotted accurately and with a neat x L – Line of best fit is drawn * equal distribution of points above and below the line, line is not too thick * follow trend instead of trying to pass through all the points S – Correct scale is used * more than ½ of the grid is used by the plotted points * no awkward scale like 3 cm rep 2 mm or 2 cm rep 3 degrees etc is used (i) Measure the gradient of the line, showing clearly on your graph how you did this. Gradient = y2 – y1 = 0.60 – 0.35 = 0.25 / 155 = 0.00161 x 2 – x1 325 - 170 Must show •Working on the graph (big dotted triangle with coordinates labelled) •Formula of gradient •Substitution •final ans to 3 s.f. (ii) Use the gradient from (i) and the extension, E, from (4) to find the value of g, using the following formula. Must show •substitution •final ans to 3 s.f. g between 9 to 11 (iii) What are the units of your value of g? [0.2 is a constant which has a unit of 1/g.] m/s2 (iv) State a precaution that you have taken to increase the accuracy of the experiment. Ensure that the oscillation is steady before timing to ensure that the period for every oscillation is consistent. Or Ensure that the spring oscillates up and down only, reject timing if it oscillate in 2 or 3 dimensions to ensure that the period for every oscillation is consistent. When stating precaution, -Be specific on what is done, do not give general comments like ‘avoid parallax error’; -Do not repeat the steps already stated in the procedure (e.g. repeat the experiment and find the average to reduce random error caused by human reaction time); -state what is being done and why it is necessary to do it.
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