An engineer investigates the elastic properties of a spring by adding various loads and measuring the extension. The experiment is repeated three times for each load.
The table below shows the engineer's results:
Load (N)\multicolumn4c∣Extension (mm)\cline2−5Test 1Test 2Test 3Mean2.03.13.33.2???4.06.36.56.46.46.09.59.79.69.68.012.712.912.812.810.015.916.116.016.0\begin{array}{|c|c|c|c|c|} \hline \mathbf{\text{Load (N)}} & \multicolumn{4}{c|}{\mathbf{\text{Extension (mm)}}} \\ \cline{2-5} & \mathbf{\text{Test 1}} & \mathbf{\text{Test 2}} & \mathbf{\text{Test 3}} & \text{Mean} \\ \hline 2.0 & 3.1 & 3.3 & 3.2 & \text{???} \\ \hline 4.0 & 6.3 & 6.5 & 6.4 & 6.4 \\ \hline 6.0 & 9.5 & 9.7 & 9.6 & 9.6 \\ \hline 8.0 & 12.7 & 12.9 & 12.8 & 12.8 \\ \hline 10.0 & 15.9 & 16.1 & 16.0 & 16.0 \\ \hline \end{array}Load (N)\cline2−52.04.06.08.010.0\multicolumn4c∣Extension (mm)Test 13.16.39.512.715.9Test 23.36.59.712.916.1Test 33.26.49.612.816.0Mean???6.49.612.816.0
Calculate the missing value of the mean extension for a load of 2.0 N2.0\text{ N}2.0 N to a suitable degree of accuracy.
A graph of Load (on the y-axis) against Mean Extension (on the x-axis) is plotted. The straight line of best fit passes through the origin (0,0)(0, 0)(0,0) and the point (16.0 mm,10.0 N)(16.0\text{ mm}, 10.0\text{ N})(16.0 mm,10.0 N).
Calculate the gradient of this line, expressing your answer in N/mm\text{N/mm}N/mm.
Use your answer to determine the spring constant of the spring in N/m\text{N/m}N/m.
The engineer says that because their repeated trials with the same method and setup gave very similar results, the experiment is reproducible. State why this statement is incorrect.
Identify one potential hazard for this experiment and describe a suitable precaution the engineer should take.
39 exam-style questions on OCR GCSE Physics Forces in action. Each one has a worked solution and a mark scheme showing where the marks go.