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.