Lecture Notes: Contact and Non-Contact Forces

Introduction to Forces

• Definition of Force
  • A force is a push or pull acting on an object due to interaction with another object.
  • Measured in newtons (N).
• Example: A hand pushing a box with a force (e.g., 5 N).
• Characteristics of Forces:
  • Magnitude (measured in newtons).
  • Direction (e.g., acting to the right).
  • Forces are vector quantities (have both magnitude and direction).

Types of Forces

• All forces can be categorized into:
  • Contact Forces
  • Non-Contact Forces

Contact Forces

• Definition: Forces where two objects are physically touching.
• Examples:
  • Friction: Resistance between surfaces in contact, e.g., a board on sand.
  • Air Resistance: Force experienced by objects when they come into contact with air particles.
  • Tension: Pulling force exerted through a rope.
  • Normal Contact Force: Also known as the reaction force.
    • Example: A rock on a table where the table exerts an equal and opposite force upwards to balance the weight of the rock.

Non-Contact Forces

• Definition: Forces that act without the need for physical contact, can act through empty space.
• Examples:
  • Gravitational Force: Attraction between objects with mass (e.g., Earth and a person).
  • Magnetic Force: Can be attractive or repulsive depending on the poles.
  • Electrostatic Force: Acts between charged objects, can also be attractive or repulsive.
• Fields of Influence: Non-contact forces act over areas around an object, known as fields.
• Characteristics: The strength of non-contact forces decreases as the distance between objects increases.

Conclusion

• This lecture covered the basic concepts of contact and non-contact forces.
• Further exploration of magnetic and electrostatic forces will be in subsequent lectures.