Exercise 3: sample answer

1. Ship's motion disturbs a pendulum. Idea: replace it with a spring-driven balance, which is not affected by gravity or direction.
2. Temperature changes the size of parts and the stiffness of the spring. Idea: use parts of different metals that cancel each other's expansion (a compensation balance).
3. Oil thickens in the cold and thins in the heat. Idea: use materials that need little or no oil, such as hardwood bearings or synthetic jewels (check).
4. The clock must run for months without being touched. Idea: a strong, steady spring with a fusee to even out the pull, and a design with few parts to wear.

Which was the hardest? A reasonable answer is temperature, because it affects almost every part of the clock at once and cannot be tested without long trials at sea. Another good answer is lubrication, because failures show up only after months of running. Either answer is acceptable if you give a reason.