Impulse and Momentum in Kinetics

Sep 30, 2024

Kinetics Lecture: Impulse and Momentum

Introduction

  • Final lecture on kinetics, focusing on impulse and momentum.
  • Important concepts for lab and exams.
  • Common understanding of momentum; impulse may be less familiar.

Newton’s Second Law

  • Formula: Force = Mass × Acceleration (F = ma).
  • Limitation: A snapshot of force, not accounting for fluctuating forces over time (e.g., jumping).

Impulse-Momentum Equation

  • Derived from Newton's Second Law.
  • Revised Formula: Impulse = Change in Momentum (Force × Time = Mass × Change in Velocity).
  • Useful for activities involving changing velocities (e.g., running, jumping).

Linear Momentum

  • Product of mass and linear velocity.
  • Greater mass or velocity increases momentum (e.g., bowling ball vs. basketball).

Impulse-Momentum Relationship

  • Practical application of Newton's Second Law.
  • Average net force over time changes an object's momentum.
  • Important for understanding real-world motions (e.g., sprinting, kicking).

Increasing/Decreasing Momentum

  • Increasing: More force or longer application time increases momentum (e.g., swinging a bat).
  • Decreasing: Longer time to apply force reduces force needed (e.g., bending knees when jumping).

Dynamics vs. Statics

  • Statics: Net forces = 0, no acceleration (equilibrium).
  • Dynamics: Involves acceleration, changing forces.

Conservation of Linear Momentum

  • Principle: Momentum is conserved if no external forces act on a system.
  • Useful for understanding collisions and impacts.

Real-world Example: Collision

  • Example of two players colliding in football.
  • Conservation of momentum predicts outcome post-collision.

Changing Momentum

  • External forces change momentum (e.g., braking a car).
  • Momentum not conserved with external forces.

Impulse

  • Force applied over time changes momentum.
  • Larger force or longer time increases impulse.

Real-world Examples of Impulse

  • Sports: Technique and timing crucial (e.g., golf swing).
  • Professional vs. amateur applications of force differ in timing.

Practice Problems

  • Example calculations for throwing a ball and applying forces over time.
  • Calculating force needed and time required for certain movements.

Application in Lab

  • Estimating jump height using impulse momentum relationship.
  • Calculating average force and time to determine jump impulse.
  • Projectile equations used to determine jump height.

Summary

  • Impulse and momentum are key concepts in real-world motion and sports.
  • Understanding the relationship between force, time, and velocity is crucial for analyzing movement.
  • Conservation of momentum helps predict outcomes in collisions.

Final Notes

  • These concepts will be revisited in lab and further lectures.
  • Practice problems and laboratory exercises will solidify understanding.