(II) A 7700-kg boxcar traveling 14 m/s strikes a second car at rest. The two stick together and move off with a speed of 5.0 m/s. What is the mass of the second car?

Answer

$14,000 \mathrm{kg}$

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Physics 101 Mechanics

Physics

Chapter 7

LINEAR MOMENTUM

Section 1

Momentum and Its Relation to Force

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Video Transcript

is this question. We have a box car that is seventy seven hundred program and it was driving at fourteen meters per second and it strikes at the second. Cried it wrist isn't after the strike. Say, move together the stick together into move at a velocity of five meters per second and were asked to find some mass off the city car stuffers on this cause this car eight ounces carpi. So come on, mate. M b What we're given initially discos Hoffer to write down what we're given before and afters collision We first collision we have and they he cause send seven hundred kilogram then we hardly eh because thirty meters per second we do not know what envious but we know the velocity is zero because it's it's rest after it's a stick together. So we know the final mess is, um, a house empty but we don't know exactly what it is, but because we do not know what envious But we know the final velocity is fine meters per second And the question did not just the direction of the velocity, but we can we can see that it will be moving in the same direction upsets. That's Todd. According to his consideration for mentions, that's the only direction it could be moving and conservation of momentum. It's right on the Christian again. Fattening supplemental is the same in this isolated system without any external forces. And I promise just trying to front pee in the show and people in eyes. Initially, we have m a feeding close and Phoebe, but we see Bebe is zero meters for second before as a condition. So we might as well just make this trunk because we know if he be a zero and DVD will be zero after he has the total mass tense, we know him a and we know he and I. We know Z. So it's easier do you fight? What autonomous is total mass seaQuest, Aunty Phoebe Both her feet And yeah, but for all of us also equals two and a plus and B. So if we would like to know what is and B, we just need to write em be because it's minus in Bay Eco's and they just hunger and they feed a over B minus and think so that's it. Here. I'm just like trying to substitute this expression here. So now we have what we want to find is a massive second car. We have envy young Annette inside and we have all the non quantities on the right hand side. And if we just plug everything in Yeah, Moqrin times or two fingers per second over five liters per second minus said, keeps us thirty thousand eight hundred sixty. Clever says it's actually massive car and we need to round it because the initial number wouldn't have only given two significant digits. So that is the round fourteen thousand kilograms that is mass of the second car out.

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