The following file contains data from a tensile test of a sample of acrylic sheet, from the same batch as was used to create the meccano pieces in your bridge kit.

You can download the data file here.Save the data to your computer, open it in a spreadsheet (e.g. Excel), and use the data to answer the following questions

What was the difference between 

• the length of the Al 6063 sample while the force in question 2(b) is being applied, and
• the length of the Al 6063 sample after the force in question 2(b) has been released?

Give your answer in mm, to at least 2 significant figures

If the screen is showing that the sample is in tension after you have mounted the sample, what can you do to release the tension?

What does an extensometer measure?

The crosshead/jaw can be adjusted while another team member is mounting the sample.

Lab coat is required for the tensile test

Safety glasses is not required if you are just observing the tensile test

Closed-toe shoes must be worn to the practical class.

g) With different loading applied a free body diagram at joint C looks like the following;

 The 20 kN and 15 kN forces represent the reaction forces at the support at C.  A method of Joints at other joints reveals forces F_BC = -10 kN (compression)  and  F_CF= 6 kN (tension). 

Calculate the value of the force F_CH  in  kN?  [2 marks]

Assume the same angles between all members as previously.