A marine researcher investigates the tension properties of an elastic polymer band designed for attaching tracking devices to marine wildlife. They measure the elongation of a standard sample under various tension forces. The experiment is repeated three times for each force.
The table below shows the researcher's results:
\begin{array}{|c|c|c|c|c|} \hline Force (N)\mathbf{\text{Force (N)}}Force (N) & \multicolumn4c∣Elongation (mm)\multicolumn{4}{c|}{\mathbf{\text{Elongation (mm)}}}\multicolumn4c∣Elongation (mm) \ \cline2−5\cline{2-5}\cline2−5 & Test 1\mathbf{\text{Test 1}}Test 1 & Test 2\mathbf{\text{Test 2}}Test 2 & Test 3\mathbf{\text{Test 3}}Test 3 & Mean\mathbf{\text{Mean}}Mean \ \hline 5.0 & 1.5 & 1.7 & 1.6 & ???\text{???}??? \ \hline 10.0 & 3.1 & 3.3 & 3.2 & 3.2 \ \hline 15.0 & 4.7 & 4.9 & 4.8 & 4.8 \ \hline 20.0 & 6.3 & 6.5 & 6.4 & 6.4 \ \hline 25.0 & 7.9 & 8.1 & 8.0 & 8.0 \ \hline \end{array}
Calculate the missing value of the mean elongation for a force of 5.0 N5.0\text{ N}5.0 N to a suitable degree of accuracy.
A graph of Force (on the y-axis) against Mean Elongation (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 (8.0 mm,25.0 N)(8.0\text{ mm}, 25.0\text{ N})(8.0 mm,25.0 N). (i) Calculate the gradient of this line, expressing your answer in N/mm\text{N/mm}N/mm. (ii) Use your answer to determine the stiffness constant of the polymer band in N/m\text{N/m}N/m.
The researcher claims that because their repeated trials with the exact same equipment, operator, and lab setup yielded highly consistent results, the experiment is reproducible. State why this statement is incorrect.
Identify one potential hazard for this experiment and describe a suitable precaution the researcher should take.