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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.
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