Work: springs, pumping and cables
Problem 5.269 · easy
A force of 30 N holds a spring stretched \frac{1}{4} m beyond its natural length. How much work does it take to stretch it from \frac{1}{5} m to \frac{2}{5} m beyond its natural length?
- Hooke's law: F(x) = kx, with x the stretch beyond natural length.Reviewed
- \[ 120 \]k from the given force and stretch (N/m).✓ Proved
- \[ \int\limits_{\frac{1}{5}}^{\frac{2}{5}} 120 x\, dx = \frac{36}{5} \]W = ∫ F(x) dx.✓ Proved
Answer \( \frac{36}{5} \approx 7.2\ \text{J} \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation.
The full receipt
| Line | Status | Checked by | Detail |
|---|---|---|---|
| 1 | Reviewed | reviewers: gpt-oss:20b, qwen3.6:27b-mlx | a sentence; read, not computed |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(lhs - rhs) reduced to 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(lhs - rhs) reduced to 0 |
| answer, a second way | ✓ Checked independently | sympy 1.14.0 + mpmath 1.3.0 | numerical quadrature |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass — The solution correctly applies Hooke's Law to determine the spring constant and then integrates the force over the specified interval to find the work done. The setup and calculations are sound.
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-10-05 — The solution correctly applies Hooke's Law to determine the spring constant and then integrates the force over the specified interval to find the work done. The setup and calculations are sound.gpt-oss:20b: pass 2026-10-05qwen3.6:27b-mlx: pass 2026-10-05 — The solution correctly applies Hooke's Law to determine the spring constant and integrates the force over the specified interval to find the work done.gpt-oss:20b: pass 2026-10-05
Proved: SymPy reduced the difference between the two sides to zero. Checked independently: a separate
method, named above, confirmed it. Checked numerically: the two sides agree at every sampled point, which is evidence,
not proof. Reviewed: a model or a person read it; that is all a sentence can have. Solution by
generator:structured/work, checked 2026-10-05 with SymPy 1.14.0.