Which statement correctly describes how gravity and weight vary with location on Earth?

Which statement correctly describes how gravity and weight vary with location on Earth?

• A. Weight is constant everywhere on Earth.
• B. Weight depends on local gravitational acceleration g, which varies with altitude and latitude.
• C. Gravity is completely uniform and does not vary with location.
• D. Weight equals mass times acceleration due to gravity only at sea level.

Answer: (B)

Gravity isn’t the same everywhere on the planet, so your weight isn’t the same everywhere either. The local gravitational acceleration, g, changes with distance from Earth's center and with the shape and rotation of the planet. If you’re higher up, you’re farther from the mass pulling you down, so g is smaller. If you’re at different latitudes, the equatorial bulge and the rotation of Earth affect how strongly gravity pulls you, and the rotation creates a outward centrifugal effect that slightly reduces your apparent weight, especially near the equator. Weight is the force gravity exerts on your mass, so it’s W = m g_eff, where g_eff is the local gravitational acceleration considering these effects. Because g_eff varies with altitude and latitude, weight varies as well. That’s why the statement that weight depends on local gravity, which changes with altitude and latitude, is the best description. The other options imply gravity or weight are constant or only apply under specific (sea-level) conditions, which isn’t accurate given how the Earth’s shape and rotation cause real variations in g and, therefore, in weight.

Gravity isn’t the same everywhere on the planet, so your weight isn’t the same everywhere either. The local gravitational acceleration, g, changes with distance from Earth's center and with the shape and rotation of the planet. If you’re higher up, you’re farther from the mass pulling you down, so g is smaller. If you’re at different latitudes, the equatorial bulge and the rotation of Earth affect how strongly gravity pulls you, and the rotation creates a outward centrifugal effect that slightly reduces your apparent weight, especially near the equator.

Weight is the force gravity exerts on your mass, so it’s W = m g_eff, where g_eff is the local gravitational acceleration considering these effects. Because g_eff varies with altitude and latitude, weight varies as well. That’s why the statement that weight depends on local gravity, which changes with altitude and latitude, is the best description.

The other options imply gravity or weight are constant or only apply under specific (sea-level) conditions, which isn’t accurate given how the Earth’s shape and rotation cause real variations in g and, therefore, in weight.