CP 08 - Tensile strength of plant fibers

Independent Variable

The length of plant string used

Dependent variable

The mass added before the string breaks

Apparatus

• Plant to test

• Cotton wool

• 2 retort stands with clamps

• Small weights - 10g

• Scalpel

• Ruler

Method

1. Use the scalpel to remove 9 fibrous strings from your plant sample, examining each one to check there are no breakages along its length and that its diameter is even.

2. On the chopping board or white tile use a ruler and scalpel to cut the 9 strings into three 10 cm, three 15 cm and three 20 cm lengths.

3. Set up the clamps and retorts as shown in the diagram with the first 10 cm string.

4. Ensure the string is properly secured with the cotton wool cushioning directly beneath it, then begin to add weights to the string, 10g at a time until the string breaks. mass.

5. Repeat step 4 with each of the other two 10 cm strings and calculate a mean mass added before the string breaks. Then repeat for the 15 cm and 20 cm lengths.

6. Plot a graph of your results.

Diagram