WEBVTT
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once again our welcome to new problem. Uh,
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this time we're dealing with physics, and in physics
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, we have Newton's laws. Eso Isaac Newton was
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a famous physicist, and he solved ah, lot
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off problems and physics using algebra and calculus. And
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Newton's first Law states that, ah, body but
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rest remains addressed or a body moving with uniforms.
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Motion continues to move with uniform motion unless compelled,
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uh, by external forces on their Newton's second law
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. Simply say's that force is the product off mass
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times acceleration, and you can extend that to mass
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times defining explorations. Final velocity minus initial velocity all
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over time. So forced times time equals two.
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Uh, and the final and the note. This
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value is called the Impulse. It's called the Impulse
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Off the Force, and it's a measure off.
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The change in momentum whereby I am the final is
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the final momentum, and M V note is the
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initial mo mentum. Um mo Mentum is the product
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of mass times velocity. That's just what momentum is
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. It's the product of most times velocity, and
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it does happen to be, uh, and the
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final envy initial. So we do have a problem
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and These are railroad problems. Uh, so we
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have a railroad hope. We have a railroad khokha
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, and obviously it's gonna have some opening somewhere.
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And all of this is just sand. This is
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sand on a theme. The it's filled with sand
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. The initial speed we not, um, is
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15 leaders a second, and this is how it's
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rolling on the trucks and this surface. The friction
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on this surface zero on the friction is zero.
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Both the kinetic friction and static friction. So this
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surfaces frictionless, frictionless office, uh, the total
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musk off the sand, plus the mask off the
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car. Mm hmm. Is the same Azaz 85,000
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kilograms. And so assume we have, Ah,
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a door that's not fully closed. So, you
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know, this is, like, a look an
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opening right here. So it's not fully closed,
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and then the sun starts to leak. So the
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sun is leaking, and after a time off,
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10 minutes at the time of 10 minutes, we've
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lost Mm. Must off. Sand lost is equivalent
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to 13,000 Philip mumps. So here's the question.
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The question is, if that's the case Mm.
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If that's the case, we wanted to time in
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, uh, the speed off. The hope wanted
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to time in the speed. So we love them
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right here. So we'll say determine determined thing,
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speed. Mm. Off the This is not 10
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minutes, but this is 20 minutes. It's time
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in this speed off the railroad. Cool. So
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this is what happens Are the surface is frictionless with
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no external forces, therefore, to move out constant
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velocity 15 m per second. Uh, railroad cool
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does not require any external forces. Well, this
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was standing forces does not require instead of saying does
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not require any external forces that does not require any
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push. Oh, cool. Um and so in
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that sense was saying Newton's first law oh, stands
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was valid on since there on no external forces acting
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on the system through the resultant false on the system
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is zero. The result and force on the system
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is zero. So if you think about the impulse
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, FD equals two m v final minus m v
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initial. This is the final momentum minus initial momentum
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. Uh, if f zero, that means that
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the change in momentum is also zero. So the
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final momentum is equal to the initial momentum and Mm
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. Since the masses. Mm, the mosque.
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This this would be the mosque before I would say
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that the total moss hmm, since the would say
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, since since the moss off the system. Alright
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, since the total most of the system on before
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was actually we don't even have to use the Newton's
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second law just by Newton's first law just by Newton's
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fastball. We can, uh, hypothesize. But
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all right, I can hypothesize that. Bye.
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Hughton's first Lou the Smart, you know velocity is
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the same. How is the initial velocity outs?
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15 m per second? Because, hmm, the
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body is moving but constant speed on a frictionless surface
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with no external interference. If there's external interference,
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then we're gonna go into Newton's second law. So
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once again, we had a problem, and in
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this problem we had a railroad car with 85,000 kg
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of weight and in 20 minutes it's losing 13,000 kg
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. But we want to find out the speed after
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these losses. It just so happens that we don't
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have any external forces based on Newton's first of all
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, and therefore the velocity will stay constant since we
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don't have external interference. But 15 m per second
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. Hope you enjoy the problem. Feel free to
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send any questions or comments and have a wonderful day
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.