A manufacturer tests two identical foam pads used to protect equipment. Each pad is initially 40.0 mm thick. Opposing forces compress each pad. After each test, the forces are removed.
| Pad | Maximum force in N\mathrm{N}N | Force–compression relationship during loading | Final unloaded thickness in mm\mathrm{mm}mm |
|---|---|---|---|
| P | 70 | Straight line through the origin up to 50 N, then curves | 40.0 |
| Q | 100 | Straight line through the origin up to 50 N, then curves | 37.0 |
A technician claims that permanent deformation begins as soon as the force–compression relationship becomes non-linear.
Explain whether the results support this claim.
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.