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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