A Level Physics Practice Exam

Where does an object's weight act through?

1. Through its outer edges

2. Through its center of mass

3. Through its center of buoyancy

4. Through its center of gravity

The correct answer is: Through its center of gravity

An object's weight acts through its center of gravity, which is the point where the entire weight of the object is concentrated. This point is significant because it is the location where gravitational forces can be considered to act, simplifying calculations involving equilibrium and motion. Center of gravity is especially relevant for uniformly dense objects where the center of gravity coincides with the center of mass. For most practical purposes, particularly in physics, the terms "center of mass" and "center of gravity" can be used interchangeably when a uniform gravitational field is present. In contrast, while the center of buoyancy is relevant for objects submerged in fluids and relates to the buoyant force, it does not apply when considering gravitational forces acting on an object's weight. Similarly, the outer edges of an object do not determine the direction or point through which its weight acts, as the weight is a force that acts through the whole mass of the object rather than localized at any single edge.