Momentum Introduction

Ch 9 Notes

Momentum

Momentum: inertia in motionρ = m v ρ (rho)units of kgm/sVECTOR QUANTITY

Inertia of an object depends on its mass AND velocity

Impulse = Change in Momentumunits of NsBased on definitions of acceleration:a = F/m & a = Δv/t so F/m = Δv/t Cross multiply to get F t = m Δv

Impulse

Impulse = Change in Momentumunits of N*s

Impulse (I) = FΔtA measure of how quickly

momentum changes.Or how quickly a force acts upon

an object.

Impulse Examples

Large Force, Little Time Little Force, Larger Time

Conservation of Momentum For closed systems, the sum of the

momenta must be conserved between the objects in the system.

Σρinitial = Σρfinal

Nonstick perfectly elasticm1v1i + m2v2i = m1v1f + m2v2f

Sticky inelasticm1v1i + m2v2i = (m1+m2) vf

Impulse Momentum Theorm

If momentum must be conserved, then…

The impulse of an object and its momentum must be conserved, so…

ρ = m v and I = FΔt Therefore: mΔv = FΔt for

objects in the same system

Momentum Example

What is the momentum of a 250kg car that is traveling at 9 m/s?

Impulse Example

What is the impulse of a ball that collides with a wall in .03s with a force of 150N?

Impulse Momentum Theorm

What is the change in momentum of an object that has collides with a wall with an impulse of .15 N*s?

Agenda 5/5

Review LOCOE Quizzes

Review Impulse and Momentum

Momentum Lab Collisions

Revenge of the Fifth

Agenda 5/6/15

Warm-Up Electrostatics

Conservation of Momentum Lab Exploding Carts!!

Change in Momentum: Collisions

Collisions

Elastic Collisions Two objects collide and

bounce off of one another Ex: Tennis ball and racket Momentum is conserved m1v1i + m2v2i = m1v1f

+ m2v2f

Collisions

Inelastic Collisions Two objects collide and stick together Two masses become one mass moving

at a slower velocity m1v1i + m2v2i = (m1+m2) vf

Example

A 2kg bowling ball is rolled into a .5kg pin. The ball is moving with a velocity of 2.5m/s and collides elastically with the pin. After the collision the ball is moving at .25 m/s. How fast was the pin moving after the collision?

Agenda 5/8/15

Circuits Warm-Up Need calculators

Momentum and Impulse Lab

Complete Collision Problems and turn in on calcs

Momentum/Impulse Quiz Monday

Safety

Wear goggles No one else should be near the table

when you chop You must chop THROUGH the board

If you stop at the board you will hurt yourself

Close your fingers when you chop If you don’t you could hurt them