Understanding Force

Basic Definition

• Force is commonly defined in textbooks as a push or pull upon an object.
• This definition may be too simplistic and doesn't fully explain the concept of force.

Misconceptions About Force

• Example: A stationary ball on the ground.
  • Misconception: No forces act on it if it doesn't move.
  • Reality: Forces are acting on it even when stationary:
    • Gravitational Force: Pulls the ball toward the Earth's center.
    • Normal Force: Ground exerts this force in the opposite direction, balancing the gravitational force.
  • Balanced forces result in a net force of zero, hence no movement.

Movement and Net Force

• For an object to move, a net force (unbalanced forces) must be present.
• Example: A person kicks a ball:
  • The ball moves because the forces are unbalanced.
  • The ball stops due to friction acting in the opposite direction to the kick.

The Role of Friction

• Friction opposes motion, causing moving objects to stop unless continuously acted upon.

Frictionless Environment Example

• On a frictionless surface with no air resistance:
  • A ball moving at a constant velocity (e.g., 2 m/s) will continue indefinitely.
  • Only gravitational and normal forces act, which balance each other.
  • If no external force acts, the motion is sustained.

Key Learnings About Force

• Stationary Object:
  • If net force is zero, it remains at rest.
• Object in Uniform Motion:
  • Continues moving at constant velocity if net force is zero.

Effect of External Force

• When an external force is applied:
  • The object will accelerate.
  • Example: If velocity increases from 2 m/s to 3 m/s due to an external force, it will continue at 3 m/s unless acted upon by another force.

Conclusion

• Force is an interaction between objects, explained by the effects observed when forces are applied.
• Further exploration of force will be covered in future sessions.