Two metal wires, R and S, are pulled in a materials test. Both wires have zero extension before the test.
| Force in N\mathrm{N}N | Extension of R in mm\mathrm{mm}mm | Extension of S in mm\mathrm{mm}mm |
|---|---|---|
| 10 | 0.3 | 0.5 |
| 20 | 0.7 | 1.0 |
| 30 | 1.4 | 1.5 |
After the force is removed, wire R has an extension of 0.2 mm and wire S has zero extension.
Which conclusion is supported by these results?
Only wire S has a directly proportional force-extension relationship, and only wire R is permanently distorted.
Both wires have directly proportional force-extension relationships, and only wire R is permanently distorted.
Only wire S has a directly proportional force-extension relationship, and neither wire is permanently distorted.
Only wire R has a directly proportional force-extension relationship, and only wire S is permanently distorted.
102 exam-style questions on Edexcel GCSE Physics 15.1 Forces and springs, covering 15.1.1 Elastic and inelastic distortion, 15.1.2 The spring constant, 15.1.3 Work done in stretching a spring, and 15.1.4 Linear and non-linear force–extension. Each one has a worked solution and a mark scheme showing where the marks go.