Momentum and CollisionsMomentum and Collisionshttp://www.youtube.com/watch?v=4ZrXUc6SA7c

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►http://www.youtube.com/watch?v=WxWHm8V4lZo&feature=related Apophis in 2029 or 2036. Apophis in 2029 or 2036.

Linear MomentumLinear Momentum

►Linear Momentum is a object with m Linear Momentum is a object with m and v.and v.

►Symbol for momentum is p.Symbol for momentum is p.►Momentum is a vector. With direction Momentum is a vector. With direction

that of velocity. that of velocity. ►Dimensions of p are m and v.Dimensions of p are m and v.►SI units of p are what?SI units of p are what?►What are some examples of p? What are some examples of p?

More Linear MomMore Linear Mom

►What has more p an object with a What has more p an object with a large m or one with a smaller mass?large m or one with a smaller mass?

►What has more p an small object with What has more p an small object with a large v or a large object with a small a large v or a large object with a small v?v?

►What are some recent examples of an What are some recent examples of an object with a large v and small m? object with a large v and small m?

►Equation for p = mv. Equation for p = mv.

Change in MomentumChange in Momentum

►A change in p requires a F during a A change in p requires a F during a change in t.change in t.

►Ft = p Ft = mvf – mvi. Impulse p theoremFt = p Ft = mvf – mvi. Impulse p theorem►Equations states that a small force over a Equations states that a small force over a

long t period produces the same change long t period produces the same change in p as a large force acting during a short in p as a large force acting during a short time.time.

►Follow through Greater change in p if Follow through Greater change in p if object in contact for a longer period of t. object in contact for a longer period of t.

►http://www.physicsclassroom.com/www.physicsclassroom.com/curriculum/momentum/mom1.pdfcurriculum/momentum/mom1.pdf

Stopping times and distanceStopping times and distance

►Depend on I=p theorem. Depend on I=p theorem.

Conservation of MomentumConservation of Momentum

►Momentum is conserved.Momentum is conserved.►http://www.physicsclassroom.com/http://www.physicsclassroom.com/

mmedia/momentum/index.cfm physics mmedia/momentum/index.cfm physics classroomclassroom

►http://www.bing.com/videos/search?http://www.bing.com/videos/search?q=car+airbag+collisions&view=detail&q=car+airbag+collisions&view=detail&mid=624655912362DA14613B6246559mid=624655912362DA14613B624655912362DA14613B&first=0&FORM=LKVR12362DA14613B&first=0&FORM=LKVR16 Car seat 16 Car seat

Conservation of Momentum Conservation of Momentum ContinuedContinued

►Mom + Mom = Mom + MomMom + Mom = Mom + Mom►MV1 + MV2 = MV1 + MV2MV1 + MV2 = MV1 + MV2►Before Col = After ColBefore Col = After Col►Two types of Collisions. Inelastic and Two types of Collisions. Inelastic and

Elastic.Elastic.►Regardless Momentum is conserved.Regardless Momentum is conserved.

Collisions Conservation of Collisions Conservation of MomentumMomentum

►Forces in real world situations are not Forces in real world situations are not constant. Always changing.constant. Always changing.

►Total p remains constant in any type Total p remains constant in any type of collision.of collision.

►Total KE is not always conserved Total KE is not always conserved because some is lost due to because some is lost due to deformation of the object, heat, sound. deformation of the object, heat, sound.

Perfectly inelastic collisionsPerfectly inelastic collisions

►When two objects collide and move as When two objects collide and move as one one

►m1v1 + m2v2 = m1v1 + m2v2m1v1 + m2v2 = m1v1 + m2v2►m1v1 + m2v2 = (m1 + m2)vm1v1 + m2v2 = (m1 + m2)v

KE not constant in inelastic KE not constant in inelastic collisionscollisions

►Total KE not constant when objects Total KE not constant when objects collide and stick together.collide and stick together.

►The reason is that in inelastic collisions The reason is that in inelastic collisions objects do not keep there shape. They objects do not keep there shape. They deform.deform.

Elastic CollisionsElastic Collisions

►Two objects collide and maintain or Two objects collide and maintain or return to their original shape. return to their original shape.

►They do not stick together. They do not stick together. ►Most collisions are not truly elastic or Most collisions are not truly elastic or

perfectly inelastic. Because energy is perfectly inelastic. Because energy is lost. lost.

►KE is conserved in elastic collisions. KE is conserved in elastic collisions.

Equation for elasticEquation for elastic

►m1v1 + m2v2 = m1v1 + m2v2m1v1 + m2v2 = m1v1 + m2v2►KE equationKE equation►½ m1v1^2 + 1/2m2v2^2 = ½ m1v1^2 + 1/2m2v2^2 =

1/2m1v1^2 + 1/2m2v2^21/2m1v1^2 + 1/2m2v2^2►Table 6-2Table 6-2

Collision labCollision lab

►Phet Lab Colorado: Collisions in one Phet Lab Colorado: Collisions in one dimension.dimension.

►http://phet.colorado.edu/sims/collision-lab/collision-lab_en.html

►Lab one►Lab two