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Newton's Laws of Motion

Jun 14, 2024

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Newton's Laws of Motion Lecture

Introduction

  • Force and motion understanding through Newton's laws.
  • Reviewed the Law of Inertia: object at rest stays at rest, and object in motion continues at constant velocity unless acted upon by a net force.
  • Focus on: Law of Acceleration and Law of Interaction.

Law of Acceleration

  • Definition: Acceleration is the rate of change of velocity.
  • Equation: ( \Sigma F = ma )
  • Proportions:
    • Directly proportional to the net force acting on it.
    • Inversely proportional to its mass.
  • Direction: Acceleration direction = net force direction.
  • Example 1: Pushing a pile of fish boxes (50kg).
    • Single person vs three people pushing.
    • Shows increase in net force increases acceleration.
  • Example 2: Pushing a boat vs fish boxes.
    • Larger mass requires more force to accelerate.
  • Units and Systems: MKS, CGS, and FPS systems.
    • MKS: Force (Newton), Mass (Kilogram), Acceleration (Meter/Second^2).
    • CGS: Force (Dyne), Mass (Gram), Acceleration (Centimeter/Second^2).
    • FPS: Force (Pound), Mass (Slug), Acceleration (Foot/Second^2).
  • Sample Problems:
    • Problem 1: 1000kg truck, acceleration 4.5m/s^2 east.
      • Solution: ( F = ma ); Net force = 4500N east.
    • Problem 2: 200g baseball, pushed with 2N.
      • Solution: Unit conversion needed, acceleration = 10m/s^2 to the right.
    • Problem 3: Box pushed with 20N and 10N opposes.
      • Solution: Net force calculation, mass found to be 6.67kg.

Force of Gravity

  • Gravitational Force:
    • Acceleration due to gravity (g) ≈ 9.8m/s^2.
    • Formula: ( F_g = mg ) where ( F_g ) = gravitational force, m = mass, g = acceleration due to gravity.
    • Example: Mass = 40kg, Weight on Earth = 392N.

Law of Interaction (Third Law)

  • Definition: For every action, there is an equal and opposite reaction.
  • Example: Pushing a wall.
    • Action force applied on the wall.
    • Reaction force exerted by the wall.

Test Questions

  1. Define inertia.
  2. Explain Newton’s First Law of Motion.
  3. Explain Newton's Second Law of Motion.
  4. Describe Newton's Third Law of Motion.
  5. Define weight.
  6. Identify which law applies to forces with equal magnitude and opposite direction.
  7. Explain which Newton's law necessitates seat belt use.
  8. Calculate the weight of a 0.200kg guava.

Conclusion

  • Completion of Newton’s laws discussion.
  • Encouragement for continuous learning and application in daily life.

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