A spring has an unstretched length of 0.100 m. A mass of 0.400 kg is attached to the spring and lowered slowly until it hangs at rest. Its length is now 0.180 m. The spring obeys Hooke's law. The gravitational field strength is 10 N/kg. Use F=kxF=kxF=kx and E=12kx2\displaystyle E=\frac{1}{2}kx^2E=21kx2. What elastic energy is stored in the spring?
0.36 J0.36\ \mathrm{J}0.36 J
0.72 J0.72\ \mathrm{J}0.72 J
0.16 J0.16\ \mathrm{J}0.16 J
0.32 J0.32\ \mathrm{J}0.32 J
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.