Momentum Physics Nov 26/27

Objectives Define momentum Define impulse and describe how it affects changes in momentum Next Class Solve for momentum and impulse Explain why an impulse is greater when an object bounces than when the same object comes to a sudden stop

Exploration Can you figure out how to catch an egg without it breaking?

What were your results? Topic What did you do to catch the egg? Did it break? Facts

Momentum Topic momentum Facts Momentum effects things in motion Inertia in motion Symbol is p p = mv – p = momentum (kg m/s) – m = mass (kg) – v = velocity (m/s) Also referred to as impulse

Reach for the Stars! Topic Momentum is a vector quantity. Why? Facts Because velocity is part of momentum which is a vector quantity The momentum is in the same direction as the velocity

Momentum with Bill Nye Bill Nye Video

More about Impulse Topic Impulse Facts Impulse is the change momentum The quantity force x time Impulse = Ft Units are Newton x seconds (Ns) a force applied for a longer time period produces more change in momentum than the same force applied briefly

The relationship between momentum and impulse Topic Momentum and impulse Facts p = mv Impulse = Ft Therefore, Ft = mv

Why? Topic Ft = mv Facts F = ma, so we can substitute for F mat = mv a = v/t, therefore substitute for a mvt = mv, the t’s cancel t Leaving you, mv = mv, which is why impulse equals momentum!

Let’s See if You Understand Topic If you know the momentum of an object, what else do you know? Facts The impulse

Something more visual Momentum Summary (until 1:30) Momentum Summary

Explore- increasing momentum? Topic If you want to hit a home run, what would you do in order for the baseball to have the greatest momentum? Facts Swing as hard as possible (force) and follow through (increases the time of contact between ball and bat) Ft

How do you increase momentum? Topic Increasing momentum Facts Apply greatest force for longest time Ft

Create your own example Topic How could you increase the momentum when hitting a volleyball? Facts

Explore- decreasing momentum? Topic What did you have to do to catch the egg without it breaking? Refer to impulse- change time or force? Facts I increased the time the egg was in contact with the plate so that the change in momentum (as it falls to zero) results in less force between the egg and the plate

How do you decrease momentum? Topic Decreasing momentum Facts 1.Increase the amount of impact time; therefore, decreasing the force 2.Maximize force; therefore, minimizing the impact time.

Reach for the Stars! Topic What is the relationship between force and time? Facts They are inversely proportional!!!

Let’s See if You Understand Topic Why is falling on a floor with more give (like carpet) less dangerous than falling on a floor with less give (like concrete)? Facts Because the floor with more give (like carpet) allows a greater time for the impulse that reduces the momentum of fall to zero. A greater time for change in momentum results in less force.

Make your own example of decreasing momentum Topic Give an example where the momentum is decreased by increasing the impact time Facts Falling into a net – Increases impact time

Make your own example of decreasing momentum Topic Give an example where to momentum is decreased by increasing the impact force Facts A karate chop on a cement block – Lots of force – Short impact time

Class work Make a plan for container that will keep your egg alive!

Closing Egg Drop Lab When dropping the egg container, it will have momentum. What should your container do in order to decrease the momentum so the egg will not break? Increase the amount of impact time; therefore, decreasing the force

Homework Bring materials to build container!!! Read and answer ques

Practice solving for momentum Topic Tiger woods hits a 0.05kg golf ball, giving it a speed of 75 m/s. What impulse does he impart to the ball. Facts KnownSolve Unknown Equation

Practice solving for momentum Topic If Tiger’s golf ball rolls onto the green 4.5 s later, what is the average force it exerted on the green. Facts KnownSolve Unknown Equation

Practice Yourself Page 101 in your textbook, numbers p = mv Impulse = Ft

Closing Topic How does impulse affect changes in momentum? Facts

Homework 1.Study the momentum notes! 2.Bring materials for egg drop lab