Short Answer
Gravity and length is the best answer.
This concept lives inside the mechanics toolkit: forces, motion, energy, momentum, and rotation. The safest way to solve it is to name the governing law first, then connect the variables in units you trust.
T = 2π√(L/g) — period depends on length L and gravitational field g, not mass or amplitude (for small swings).
Why This Answer Is Correct
This is a Medium-level question in Classical Mechanics. The prompt is really testing whether you can connect the concept to its defining physical relationship instead of picking a nearby-but-wrong term.
Mechanics questions usually become easier once you identify whether the problem is about force balance, kinematics, energy, or conservation.
Choices At A Glance
- A. Bob mass
- B. Amplitude
- C. Gravity and length
- D. Material
When similar options appear on an exam, eliminate the ones that break the core law, use the wrong units, or confuse a definition with a consequence.
Topic Snapshot
Topic: Classical Mechanics
Difficulty: Medium
Best next move: Re-state the governing law in your own words, then solve one more example from the same topic before moving on.