An engineer is testing composite bungee-cord linkages joined together by metal carabiners. She stretches different linkages horizontally against a steel rule using a tensioning winch.
For each linkage, she records:
Then she calculates the difference in length for each linkage.
The table below shows some of her results.
| Number of bungee-cord elements | Length when tension = 8.0 N8.0\text{ N}8.0 N (cm) | Length when tension = 4.0 N4.0\text{ N}4.0 N (cm) | Difference in length (cm) |
|---|---|---|---|
| 1 | 24.5 | 21.8 | 2.7 |
| 2 | 51.2 | 45.8 | 5.4 |
| 3 | 78.0 | 69.9 | 8.1 |
| 4 | 104.9 | 94.1 | 10.8 |
| 5 | 131.7 | 118.2 | [Missing] |
Calculate the missing difference in length.
The engineer measures the length of one carabiner from the linkage against the steel rule.
Estimate the length of this carabiner.
Suggest two ways that the engineer could improve her measuring technique when measuring the linkages.
