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Physics · Forces · Hooke's law
Hooke's law for a helical spring
Hang masses one by one from a vertical spring. Use a metre rule to measure how far the pointer has moved each time. Plot F against extension — within the elastic limit, you get a straight line through the origin. The gradient gives the spring constant.
F = 0.0 N · x = 0.00 cm
Results table
| F (N) | x (cm) | k (N/m) |
|---|---|---|
| 0.0 | — | — |
| 0.5 | — | — |
| 1.0 | — | — |
| 1.5 | — | — |
| 2.0 | — | — |
| 2.5 | — | — |
| 3.0 | — | — |
| 4.0 | — | — |
| 5.0 | — | — |
| 6.0 | — | — |
| 7.0 | — | — |
| 8.0 | — | — |
Plot · F vs extension
Linear region: k = 25 N/m. Beyond ~ 6 N the spring deforms plastically.
Exam-style questions
1. Hooke's Law states:
2. On the F-vs-extension graph, what does the GRADIENT represent?
3. After the elastic LIMIT is exceeded, why does the line curve?
4. A 200 g mass is hung on a spring of stiffness 50 N/m. Extension?