Tr.Linn Sandar Win(Physics)
Centre of Gravity
Definition:

The centre of gravity of an object is the point where the entire weight of the object
appears to act, regardless of its position.
Key Points:

Uniform objects (like a regular ruler or a symmetrical shape) have their centre of
gravity at the geometric center.

Irregular objects (like a hammer or a human body) have their centre of gravity at a
point that depends on their shape and mass distribution.

The centre of gravity can sometimes be located outside the physical material of the
object (for example, in a ring or hollow object).
Practical Importance:

If the centre of gravity is above the base of an object and within its support area, the
object remains stable.

If the centre of gravity shifts outside the base (due to tilting), the object will topple.
Examples:

When standing, the centre of gravity of a person is in their abdomen.

Lowering the centre of gravity (e.g., bending down) increases stability.
2. Centripetal Force
Definition:

Centripetal force is the force that keeps an object moving in a circular path. It acts
towards the center of the circle or curved path.
Key Points:

Centripetal force is not a type of force on its own. It is provided by other forces, such
as tension, gravity, friction, or normal contact forces.

Without centripetal force, an object would continue in a straight line due to inertia
(Newton's First Law).
Examples:

For a car moving around a curve, friction between the tires and the road provides
the centripetal force.

For an object attached to a string and swung in a circle, tension in the string provides
the centripetal force.
Effects of Increasing Speed or Decreasing Radius:

If an object moves faster or if the radius of the circular path decreases, the required
centripetal force increases. This means there must be greater tension, friction, or
another force to keep the object moving in a circular path.
3. Stability
Definition:

Stability refers to an object's ability to remain upright and resist toppling.
Factors Affecting Stability:

Centre of Gravity: The lower the centre of gravity, the more stable the object.

Base Area: The larger the base area, the more stable the object.

Line of Action: Stability depends on whether the line of action (an imaginary line
through the centre of gravity) falls within the base of the object.
Types of Stability:

Stable Equilibrium: If displaced, the object returns to its original position. (e.g., a
cone resting on its wide base).

Unstable Equilibrium: If displaced, the object continues to move away from its
original position (e.g., a cone balanced on its tip).

Neutral Equilibrium: If displaced, the object stays in its new position (e.g., a ball on
a flat surface).
Applications in Real Life:

Vehicles have a low centre of gravity and wide base to prevent tipping.

Structures, like buildings, are designed with a wide base to enhance stability.
Example:

A double-decker bus has a higher center of gravity than a regular car, which is why it
may tip more easily around sharp turns unless its design ensures stability with a wide
enough base.
Summary

Centre of Gravity is the point where the weight of an object acts and determines its
stability. A low center of gravity increases stability.

Centripetal Force is the force acting towards the center of a circular path that keeps
an object moving in a circle.

Stability is influenced by the center of gravity and the base of an object. A wide base
and low center of gravity enhance stability, reducing the likelihood of toppling.