Brainlag PlusElastic and inelastic deformation, F = ke and the limit of proportionality, elastic potential energy ½ke², and the required practical on a spring.
Stretch it and let go
To stretch, squash or bend an object you need more than one force on it; one force alone would just move it.
- Elastic deformation: it goes back to its original shape and length when the forces are removed (a rubber band, a squeezed tennis ball).
- Inelastic deformation: it stays changed (a crushed can, squashed modelling clay).
For a spring, the extension is directly proportional to the force, up to a point:
force = spring constant × extension
F = k e
F in N, k in N/m, e in m. AQA and OCR: recall. Edexcel writes it F = k × x: recall too. The same equation works for compression.
- A spring with k = 40 N/m is stretched 5 cm
- e = 5 ÷ 100 = 0.05 m
- F = 40 × 0.05 = 2 N
Extension is the increase in length: new length − original length. It is not the new length.
The rest of this lesson and its 11 practice questions are in Plus.
Screen 1 of 6, free to read.
- 11 exam-style questions, marked as you go, each with a worked solution
- The Mass on a spring simulation beside every question
- Anything you get wrong is saved to your flashcards