Laws of Motion - Part 1

Topics Covered

• Introduction
• Aristotle's Fallacy
• The Law of Inertia
• Newton's First Law of Motion
• Newton's Second Law of Motion
• Newton's Third Law of Motion
• Conservation of Momentum
• Equilibrium of a Particle
• Common Forces in Mechanics
• Circular Motion
• Solving Problems in Mechanics

Introduction to Motion

• Motion is a change in the position of an object with respect to time.
• An external force is needed to make a stationary body move.
  • Example: A ball stays at rest until a force is applied.
• An external force is also needed to stop a moving body.

Uniform Motion

• Uniform motion: a body moving with constant velocity.
• In uniform motion, the velocity of the body remains the same throughout.
• The physics behind uniform motion involves understanding the forces at play.

Aristotle's Law of Uniform Motion

• Proposed that an external force is required to keep a body in uniform motion.
• Based on observations of a moving box tied to a string and a person dragging it.
  • When the force (string tension) was removed, the box stopped moving.

Aristotle's Fallacy

• Aristotle's conclusion was proven false over time.
• The observed scenario involved friction:
  • A force of friction acts at the surface of contact between the box and the floor.
  • Friction opposes motion.
• When external force is greater than friction, the body moves.
• Upon removing the external force, friction stops the motion.

Conclusion

• An external force is needed to keep a body in uniform motion only if resistive forces like friction or viscous forces are present.

Resources

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