Richer's observation of pendulum clocks suggested what about Earth's shape?

• A. Flattening at the equator
• B. Flattening at the poles
• C. Spherical
• D. Irregular

Answer: (B)

The test targets how local gravity measured by pendulums reveals the shape of the Earth. A simple pendulum’s period is T ≈ 2π√(L/g), so if gravity g is smaller, the pendulum ticks more slowly (its period is longer). Richer compared pendulum clocks at different latitudes and found a systematic variation: clocks near the equator ran slower than those near the poles. That pattern fits a rotating body that bulges at the equator because the centrifugal effect of rotation reduces effective gravity more at the equator, and the radius at the equator is larger. In other words, the Earth is not a perfect sphere but flattened at the poles (an oblate spheroid) with an equatorial bulge.