The method and the results are on the Young modulus lab. Do the analysis yourself first, then check the answers below.
Quick answer: Hooke's law says extension is proportional to force (F = kx) up to the limit of proportionality. These answers go with the Physics 11-12 lab on Young modulus: the graph, the calculations, the uncertainties and the conclusion explained, for all 8 analysis questions.
So the model answers use the sample results above. Also, your values will differ slightly, but the graph should be a straight line through the origin and your Young modulus should lie near 200 GPa for steel.
Level: Physics grades 11-12 (A Level · IB · Class 11-12) · Curriculum: A Level 3.4.2
E = 15621.019 × 2.50 ÷ 0.000 = 198892992577.260 Pa (199 GPa), close to the accepted value for steel.
Question 6 Uncertainty
First, diameter: 0.01 ÷ 0.50 = 2 %. Area uncertainty = 2 × 2 = 4 %, so E has an uncertainty of about 4 % from this source, the largest in the experiment.
Question 7 Stored energy
E = ½Fx = ½ × 29.43 × 1.88 × 10⁻³ = 0.0277 J.
Question 8 Improvements
For example, both give a larger extension for the same load, so the percentage error in the small length x falls. Also, a reference wire carrying a constant load next to the test wire cancels the effect of temperature changes and sagging of the support. Then, take readings on unloading as well, to check that you have not passed the elastic limit.
