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M o m e n t u m
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05-Jan-2016
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Transcript of M o m e n t u m Momentum is… Inertia in motion Mass x Velocity.

• M o m e n t u m

• Momentum isInertia in motionMass x Velocity

• Creating MomentumGreater Force = Greater MomentumForce creates acceleration, so pushing harder makes you go faster.

• Impulse isForce applied x Time appliedChange in MomentumTherefore(mv) = Ft

• Impulse isCommonly confused with impact (be careful)The force appliedDetermined by solving the equation for force

• MomentumIncreasing Momentum:Increase force or timeGreatest momentum:Big force for big time

• MomentumDecreasing MomentumWhen you stop you lose all of your momentum impulse is same no matter how you stopMore time means less force (haystack)Less time means more force (brick wall)

• A Picture is Worth a Thousand WordsMan moves back, increasing time and decreasing forceMan leans in, decreasing time and increasing force

• BouncingWhen something bounces the impulse is greater because you bring velocity to 0 and then increase it the other way

• Action Reaction PairsAgainEvery action has an equal and opposite reactionThere are internal and external forces for every systemThe parts of an action reaction pair can be any of the following:Both internalBoth externalOne internal, one external

• How does Action/Reaction relate to MomentumForces that create movement must come from outside of the systemAction/Reaction both within the system cancel outFor movement one part of action/reaction pair must be within system and one outside.

• Does Direction Matter?Momentum is a vector quantity it has direction. Because of this two momentums that are of equal magnitude and in opposite directions cancel each other out. *if there is no NET force or NET impulse acting on a system, the momentum of that system cannot change at all*

• Law of ConservationThe law of conservation of momentum says: in the absence of an external force, the momentum of a system remains unchanged.

• DemonstrationWatch the movement of the person at the front of the room as they throw the ball.Was there movement of the ball?Was there movement of the personIs momentum conserved?Is momentum a vector quantity?

• A few more examplesConservation of momentum can also be shown with moving objects that undergo a weight change.The following examples show a freight train that has weight added to it while it is moving notice the change in velocity that occur with the weight increaseAre mass and velocity proportional or inversely proportional?

• Big Cart, Little Brick

• Little Cart, Big Brick

• The Fish Example Part #1

• The Fish Example Part #2

• Conservation in CollisionsNet Momentum Before = Net Momentum After Friction is usually considered to be negligible during the collision itself

• Collision TypesElastic collisions objects are not deformed or attached and dont generate heat or sound.Inelastic collisions colliding objects become tangled or coupled together. They still follow the law of conservation, but after the collision they are attached to each other.

• Inelastic Collision Example #1This demonstration illustrates an astronaut in a frictionless environment undergoing an inelastic collision with another astronaut

• Inelastic Collision Example #2

• Inelastic Collision Example #3

• Inelastic Collision Example #4

• Inelastic Collision Example #5

• Elastic Collision Example #1

• Elastic Collision Example #2

• Elastic Collision Example #3

• Look at the difference

• Look at the difference

• Look at the difference

• Momentum VectorsMomentum vectors combine like all other vectors.When looking at the vectors involved in a collision the vector(s) before and after the collision must have the same resultant.

• Vector Collision Example