Defining the Center of Gravity
The center of gravity (CG) of an object is the average location of its weight. It is the single point where the entire force of gravity can be considered to act on the object for the purpose of analyzing forces and torques. An object suspended from this point will be perfectly balanced.
Section 2: Center of Gravity vs. Center of Mass
While often used interchangeably, the center of gravity and the center of mass are slightly different. The center of mass is the average position of all the mass in an object, while the center of gravity is the average position of its weight. In a uniform gravitational field, like that experienced by most objects near the Earth's surface, these two points are effectively identical. A difference only arises in a non-uniform gravitational field, where the CG shifts slightly closer to the stronger gravitational pull.
Section 3: A Practical Example
Imagine trying to balance a pencil horizontally on your finger. The one specific point where it balances without tipping is its center of gravity. At this point, the gravitational force pulling down on one side is perfectly balanced by the force pulling down on the other, resulting in zero net torque. For a uniform pencil, this point is at its geometric center.
Section 4: Importance in Stability
The concept of the center of gravity is fundamental to understanding stability. An object is stable as long as its center of gravity is located directly above its base of support. For example, a sports car is designed with a very low center of gravity to make it more stable and less likely to roll over during high-speed turns.