Overview
This lecture explains the concept of the center of mass, how it changes in humans and objects, factors that affect its position, and its relationship to stability in sports and movement.
Center of Mass: Definition and Characteristics
- The center of mass is the point in an object where mass is distributed evenly in all directions.
- In a uniform object, the center of mass is at the geometric center.
- In humans, the center of mass is usually around the navel but can shift with changes in body position.
- The center of mass is an imaginary point determined by the distribution of mass and can move as body parts move.
Factors Affecting Center of Mass
- Distribution of mass changes the center of mass position; moving limbs shifts the center of mass.
- Leaning forward lowers and moves the center of mass forward.
- Lifting a limb moves the center of mass toward the new mass location.
- Uniform objects (like a discus) have a fixed center of mass at their center.
Examples in Sport
- Athletes’ center of mass moves according to their body and limb positions and any equipment's mass.
- Adding a heavy object above the body (e.g., barbell) raises the center of mass, sometimes to a point outside the actual body.
- Light objects (like a golf club) have less influence; center of mass remains closer to the body’s core.
Stability and Center of Mass
- Higher center of mass = less stability; lower center of mass = more stability.
- Greater mass increases stability (heavier athletes are harder to knock over).
- A broader base of support (wider stance or more contact points) increases stability.
- Line of gravity (vertical line from center of mass) should fall within the base of support for maximum stability.
- If line of gravity moves outside the base, the object or person becomes unstable.
Key Terms & Definitions
- Center of Mass — The point where an object's mass is evenly distributed in all directions.
- Base of Support — The area beneath an object or person that includes every point of contact with the supporting surface.
- Line of Gravity — An imaginary vertical line that passes through the center of mass down to the base of support.
- Stability — The resistance to being toppled or moved from position.
Action Items / Next Steps
- Try identifying the center of mass in various sporting positions or images, using the above principles.
- Review the four main factors affecting stability and be able to apply them to real-life examples.