# momentum momentum and collisions momentum banging things around

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Post on 17-Jan-2016

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• Momentum and CollisionsBanging things around

• MomentumImpact or product of mass and velocityRepresented by the variable rFormula r = m vUnits are kg m/s

• MOMENTUM IS MASS TIMES VELOCITYMore mass means more impactWhat has more impact rolling a pingpong ball or bowling ball?More speed means more impactwhat has more impact -catching a tossed ball or line drive?

• ImpulseThe change in momentumDetermined by the amount of force for how longFormula is Dp= FtClassic example is seatbelt vs dashboard.Seatbelt means slower stop or less forceDashboard means faster stop or more force

• Newtons Laws of MotionChange in momentum occurs when force is applied. 2nd For every force applied to an object, it applies each force back. 3rd

• Conservation of MomentumMomentum cannot be created or destroyedThe results of any collision will not change the system momentumTwo objects pushing off each other will have the same total momentum as before the action

• CollisionsThree types of collisionsExplosionsInelastic collisionsElastic collisionsMomentum is always conserved

• ExplosionsExplosions are collisions where the objects begin as one and then separate into many objects traveling in different directions.All collisions begin with determining the masses involved in the collision. We designate these as m1 and m2.In an explosion, these two masses are added together before the explosion. And counted separately after the explosions.

• After the ExplosionThe sum of the momentums after the explosion must equal the sum of the momentums before the explosion.(m1 + m2)v = m1v1 + m2v2

Dont forget positive and negative directions.

• Example #1A 40-kg boy is sitting on a frozen pond holding a 4-kg book. The ice is very slick and he cannot get off the ice. If he throws the book at 6 m/s. How fast will he travel in the opposite direction?M1 = 40 kg M2 = 4 kg MT = 44 kg V2 = 6 m/s vT = 0 m/s (m1 + m2)vT = m1v1 + m2v2

• Inelastic collisionsObjects collide and continue as one object joined like two trains hooked together or a receiver catching a football.Formula is m1v1 + m2v2 = (mT)vT

• Example #2Sante throws a 20-kg medicine ball at 10 m/s to his friend Frankie weighing a hefty 100 kgs who is moving away from Sante at 2 m/s. Somehow, Santee catches the ball and falls forward. What speed does he fall forward?M1 = 20 kg M2 = 100 kg MT = 120 kgV1= 10 m/s V2 = 2 m/s vT = ? m/s

• Elastic collisionsObjects collide and then bounce off each other.Formula is:m1v1 + m2v2 = m1v1 + m2v2

• Example #3Two 200 kg bumper cars race towards each other at 10 m/s and 15 m/s. After the bump, the slower car moves away at a velocity of 12 m/s. What is the velocity of the faster car?m1 = 200kgm2 = 200 kgV1 = 10 m/s v2 = -15 m/s V1 =