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All right impulse and newton's second law the best pairing

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since pb met jay did you fire him over when

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and where A sound for buoyancy girl and seeing their

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kids all right you're in second launching for men and

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a funny thing emoji rico's graphic impulsive way her pg

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thirteen site way legal we do ok moving on every

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sport involves physics just think of the parappa ulla of

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a basketball when steph curry shoots a halfcourt buzzer beater

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for how when ah hockey player is checked into the

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boards the boards push back on the player just as

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hard as he slams into them or how the acceleration

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of gravity can really ruin a gymnast day in their

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most sports fans don't think about any of that stuff

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when they're watching the game but if you're a physicist

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while sometimes it feels like all you can see is

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physics not ghosts but when you're actually playing a sport

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you're going to be in big trouble if you've got

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physics on your brain like when you're standing in the

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batter's box looking to hit a walk off home run

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well if you're thinking about how your bat's going to

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change the balls Momentum Chances are pretty good that the

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only thing you'll be hitting our some molecules in the

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air But once you start thinking about this stuff well

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it's hard to stop After all the system between the

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batter the baseball bat and the ball itself is about

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as close is will come to having a closed system

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here on earth In physics terms a closed system is

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where no matter enters or leaves the system and there

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are no effects from forces outside of the system Got

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that All right Well if i'm trying to catch a

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foul ball and some jerk in the stands feels a

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soda on me He's just introduced some matter into the

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system made up of me and the ball Some very

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cold sticky matter And i'm not happy about it All

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right Well even in the system when i'm up to

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bat there is still the force of gravity that's pulling

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on everything And everyone on the ball also has to

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deal with drag In fact it's pretty much impossible to

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find a true closed system Of course if you could

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consider the whole universe to be one big fat close

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System Well that'd be a different thing but you hate

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to see the equation for conservation of momentum in that

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system Pretty big Well here on planet earth many things

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can enter into a closed system Like the force of

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friction We can all use sorts of goop to reduce

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friction Yeah but we could never make it go away

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completely And if you go bowling underwater while you're gonna

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be dealing with drag and buoyancy so if you're hoping

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to get a strike in the bikini bottom bowling alley

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when well it'll take a lot more room than on

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dry land So how do we figure out mo mentum

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when there's an outside force messing with it Well luckily

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for us some guy named isaac newton came up with

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a way that can help Newton's second law of motion

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tells us that if an unbalanced force is applied to

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an object that object will experience acceleration Will this law

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boils down one simple equation That equation says that the

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force equals mass times acceleration We can tinker around with

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this equation to show just how force and mo mentum

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get along Alright now buckle up This might be a

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bumpy ride Like we said we've got one of newton's

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greatest hits Force equals mass times acceleration All right well

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what is acceleration Acceleration is the change in velocity over

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the change in time And get that little triangle there

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Delta means change in whatever So let's get rid of

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a and put this thing into our force equation instead

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Okay now how do we calculate change in velocity It's

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Not too hard We just subtract the initial velocity from

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the final velocity so we can add that into our

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equation too So now our equation for force looks like

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this force equals mass times final velocity minus initial velocity

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over the change in time Kick our algebra skills into

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another gear and use the distributive property for that parent

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medical Just in case you're having a bad math day

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which hey happens to the best of us The distributive

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property means that when we have a parenthetical where addition

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or subtraction is being done and we're multiplying the result

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by something outside the parentheses were gonna multiply that outside

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term by each of the terms inside and then ditch

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the parentheses altogether So instead of mass times the result

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of final velocity minus initial velocity we can change it

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to mass times final velocity minus mass times initial velocity

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got all that so we're distributing the mass within the

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parent medical Okay great fun little math trick but what's

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the point Well we have mass multiplied by velocity In

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fact we have that twice And what is mass times

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velocity It's momenta More mojo more technically speaking So now

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we can swap out the m v stuff and put

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in momentum And instead of just saying final momenta minus

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initial moment and we can call it the change in

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mo mentum so now we have a whole new equation

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for force to go along with the old school f

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equals m a force equals the change in mo mentum

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over the change in time and this new equation will

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definitely come in handy But we can also rearrange the

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new equation assault for the change in momentum Change of

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momentum equals force times change in time I don't let

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anyone tell you that math and physics aren't creative it's

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like people who don't think baseball's creative sometimes you gotta

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find a new way to avoid getting tagged out like

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that right Well it's the same in science Creativity is

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huge thing way have to figure out ways to get

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from point a to point Q You can't just sling

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the alphabet song under our breath to figure out how

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to get there either But the other important thing is

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this change in momentum right here Well changing mo mentum

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is important because it happens all the time Momentum is

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changing everywhere You look okay If you're not looking at

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your cat sleeping in the sun where it maybe not

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But you might look out your window and see car

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slowing down at a stop sign or birds picking up

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momentum as they fly off three brands or might see

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the left fielder's momentous change very suddenly when he runs

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into the shortstop there Changing mo mentum is so important

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that it has its own names called impulse has its

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own symbol to jay Well you know impulse starts with

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a j jj impulse like that How you remember it

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Look these symbols are always gonna make sense Just roll

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with impulse is the measure of force applied over time

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so it makes sense of units for impulse are newton

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seconds or to break it down to base units Units

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for impulse are kilogram meters per second just like mo

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mentum Yeah because you know it is mo mentum or

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at least the change in mo mentum And because impulses

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force applied over time we can slap it onto a

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graph The y axis is the force in the x

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axis is the time like you might have seen on

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other graphs Such a velocity versus time Here's graph for

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a constant force flight over specific amount of time Let's

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look at all this green area right here under the

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line Don't get too excited This crap isn't going to

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reveal the meaning of life Where is money python when

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you need him it's just a rectangle And like any

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other rectangle we can find its area with a simple

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formula Yeah Base times height Remember that from like third

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grade Well what is the height represent in this green

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shape That would be force And the base is time

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We'll force times Time is impulse So the area under

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the line on our graph equals the total impulse we

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knew Geometry class Would come in handy someday All right

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Well what if we don't have constant force That's Harder

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Well here's a graph for force that decreases at a

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constant rate Same deal We find the area of everything

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under the line and here we just use the formula

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for the area of a right triangle Eight times be

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divided by two Well anytime we apply a net force

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to an object over any span of time the objects

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acceleration will change anytime acceleration changes Velocity will change in

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anytime velocity changes Mo mentum will change All of these

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things are our separate but related to each other And

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in the real world forces pretty much always applied over

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a span of time That span might be tiny like

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when a baseball hits a fast the ball in the

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bat might only be in contact for a millisecond but

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that still counts is a time span in physics but

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most time spans air a lot longer than that Like

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if we floor the gas pedal for five seconds in

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our car or even when my feet hit the ground

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is i round second base and it applies to negative

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acceleration to like When our center fielder runs into a

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wall trying to make it a catch In fact in

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our impulse equation the force has a specific name The

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force of impact and the relationship between changing mo mentum

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in time determines just how hard that impact will be

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In fact what makes something soft is completely linked to

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changing momentum Let's look back at our center fielder here

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Well you know he's getting to know the wall there

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likes a great defender but he's going to get hurt

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if he keeps on doing that or have to move

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to game of thrones and try something with white walker

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is doing that thing Yeah all right Well the wall

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has a little padding to soften the blow but trust

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me it doesn't feel too good Let's Say my kind

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of law Save nine meters a second right before he

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hits the wall and he has a mass of ninety

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kilograms So right before he makes impact his momentum is

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eight hundred ten kilogram meters per second What's his momentum

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after he hits the wall Really kind of bounces off

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of it So there's negative momentum here Walk it off

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mike But there Will be a point in this crash

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where his velocity reaches zero meters A second and that's

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what we're looking for Shmoop so the change in momentum

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will be negative Eight hundred ten kilogram meters per second

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and let's say it takes a tenth of a second

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for this change to be complete So what's the force

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of the impact well we just rearrange our impulse equation

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to solve for force before sequels impulse divided by time

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Oh and we're not i'm gonna worry about having a

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negative momentum We'll just use the absolute value Eight nine

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and ten kilogram meters per second Invited by point One

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seconds gives us a force of eighty one hundred newton's

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out No wonder mike still down for the count after

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seeing that nasty collision the grounds crew takes pity on

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poor mike They cover the outfield wall with a few

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layers of bubble wrap because bubble wrap sauce that makes

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a change in momentum take a longer amount of time

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So now instead of going from full speed to no

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speeding point one seconds it'll taking half a second Well

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how does that affect the force of the impact Wow

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reduces it to one fifth of what it was Well

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the new forces sixteen hundred twenty newtons which might not

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feel great but it's a lot less likely to put

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you on the permanent disabled list but this is why

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most safety features in your car are meant to give

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your moment and more time to reach zero that's what

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airbags do people and crumple zones crumple zones air part

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of your car that our mental collapse on impact by

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collapsing they're distributing the mo mentum change in a crash

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over a longer period of time than a rigid structure

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would see knowing newtonian physics can help save lives And

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just in case you want to prove it for yourself

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go stand on your bed and then fall over on

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your mattress kind of fun right now Do that on

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the floor a lot less fun right Don't actually do

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this by the way our lawyers just made us say

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that Sorry Consider it more of a thought Experiment people

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Physics is great but not worth breaking ribs over All

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right well just remember even though the real world situations

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are more complicated than ideal closed systems we still have

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the tools to make sense of them The more equations

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we know the more we're able to mess around with

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them to make them do What we want him to

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do so don't be afraid to breaking equation down to

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its components and then build those back up in different

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ways And don't let all this force of impact stuff

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scare you too much Sure it can be a mildly

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terrifying thing to think about a big change in mo

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mentum over a super short period of time But we

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can do things to slow that impact down Like you

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know when i lay down a bunt i'm increasing the

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time that force is applied to work in my favor

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And hey maybe instead of always trying to hit a

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home run i'll see if they have any of that

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bubble wrap The left over there Yeah they'll never see 00:12:06.739 --> [endTime] this one coming

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