An engineer is calibrating a heavy-duty seismic dampening spring in a structural testing rig.
State the two physical measurements that must be made to determine the extension of this spring when a 2.5 kN2.5\text{ kN}2.5 kN calibration load is suspended from it.
23 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.