What is the center of gravity?

• A. The point where gravity acts on the object's mass
• B. The point at which an object's mass is concentrated
• C. The geometric center of the object
• D. The point where weight is zero

Answer: (A)

Center of gravity is the point at which the total gravitational force on the body can be considered to act. In a uniform gravity field this point coincides with the center of mass—the average position of all the mass. That’s why it’s described as the spot where gravity acts on the object's mass: all the weight of the body can be thought of as acting from that single point.

This isn’t necessarily the same as the geometric center, which is just about shape and layout; the center of gravity depends on how mass is distributed. It also isn’t the point where weight is zero—gravity acts everywhere (unless you’re in a zero-gravity environment), but the resultant weight can be considered to act at the center of gravity.

So you’d locate it by thinking where the body would balance under gravity—the point about which all the weight effectively acts.