What is force?

1. Definition of Force

• Force is a push or pull exerted on an object when it interacts with another object.
• It can cause changes in:
  • Shape of an object.
  • State of rest or motion.
  • Velocity (speed and direction).
  • Acceleration of an object.

2. Force as a Vector Quantity

• Force $(\vec{F})$ has both magnitude (size) and direction.
• Represented using an arrow in a vector diagram:
  • Arrow length = magnitude of force.
  • Arrow direction = direction of force.
• SI Unit: Newton (N).

3. Types of Forces

Contact Forces (Objects must touch)

• Friction: Opposes motion between surfaces.
• Normal force: Support force exerted by a surface.

Non-Contact Forces (Act over a distance)

• Gravitational force: Pulls objects towards each other.
• Electrostatic force: Attraction or repulsion between charged particles.
• Magnetic force: Attraction or repulsion between magnets.

4. Notation for Force

• Example: 12N to the right represents a force of 12 Newtons acting towards the right.
• If no arrow is present, only the magnitude is given.