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All right well here's your Shmoop du jour brought to you by collisions [Two cars collide with each other]

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physicists are always dealing with collisions sometimes that collision is

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their head colliding with a wall over and over again trust me i have been there a [Physicist repeatedly banging his head on a chalkboard]

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particle with mass 1.5 grams moves with a velocity of negative 2 meters a second

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when it encounters a three gram particle moving to the left at a velocity of 4

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meters per second the two particles stick together and continue to move what

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is their combined velocity here are choices [Muttering of potential answers]

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Alright, well two particles collide stick together

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that's right we're dealing with an inelastic collision and we're stoked [Two particles colliding and sticking together]

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like a dream come true granted we have strange dreams there was

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this one where we were riding a dinosaur into a tunnel and never mind actually [Two people riding on a dinosaur into a tunnel]

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yeah, let's just get the question all right when we're dealing with an

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inelastic collision like this we have to remember that momentum is always

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conserved it's like there's a law about it or something so the total momentum of

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two particles before the collision has to equal the total momentum of the

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particles after the collision and we know that momentum equals mass times [Two particles stuck together above a definition of momentum]

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velocity we'll call these particles one and two - that's creative right well here's

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the equation this says that mass times velocity of particle 1 plus the mass

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times velocity of particle 2 equals the sum of the mass of both particles times [equation for the velocity of two particles]

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the final velocity we can flip going to decide which particle in this problem is

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1 and which is 2 we'll say the particle with the negative velocity is numero uno

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and now we can plug in the numbers 1.5 grams times negative 2 meters a second

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Plus 3 grams times 4 B to the second equals 4.5 grams times final velocity

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well solve them for final velocity gives us answer of 2 meters of seconds and the [equation filled in with the mass and velocity readings]

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answer B is correct if you ever feel like banging your head against a wall

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just stop take a few deep breaths and maybe take a study break because [woman stops a man from beating his head against a wall]

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studying physics can get frustrating sometimes but studying physics with a

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concussion, well that won't work yeah [Boy studying physics falls off chair]

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