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ten nine eight we have a go for main

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engine start we have main engine start

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four three two one

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bill and liftoff liftoff of the space

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discover a performance nominal Roger

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how's the picture cover back Kevin great

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picture hello and welcome to the flight

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deck of discovery or 260 kilometres

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above the surface of the earth traveling

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at 8 kilometers per second if I look out

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the window I can see a light nice to you

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huh what's this

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hey macadamia nut must be lunch

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banana pudding this must be dessert one

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of the fun things about flying in space

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is that things float that's because we

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are in a freefall orbit about the earth

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the Space Shuttle Orbiter myself the nut

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and my pudding are all falling together

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we're weightless soft this can of

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pudding is weightless why did it hurt

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and hit my head the answer to this

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question requires a little research Wow

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let's imagine that I can send this nut

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and this can down to a laboratory on

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as you can see the can of pudding weighs

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100 times more than that but weight can

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be confusing because weight depends on

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where you do the weighing on the moon

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the nut and the can weigh only 1/6 of

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what they do here on earth and here in

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orbit they both weigh the same zero so

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why is that it's because weight depends

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upon the gravitational pull exerted on

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objects the earth is very big so its

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gravitational pull is very strong the

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moon is much smaller so its

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gravitational pull is weak and objects

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weigh much less here on earth were in

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freefall and that makes it seem like

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there's no gravity at all so objects

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have different weight depending upon

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where they are well then what does that

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have to do with the bump on my head the

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answer lies in the fact that even though

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the pudding can has no weight it does

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have mass mass is that not a matter that

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is packed into an object all objects in

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the universe have mass weight can change

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but not mass the mass of this nut and of

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this pudding can remains the same no

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matter where they are in the universe

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even here on the orbiter the can of

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pudding has more mass in the nut so it

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hit me with more force so why have we

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spent all this time explaining mass to

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you well it's because you have to

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understand the concept of mass in order

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to understand Sir Isaac Newton's three

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laws of motion and that is what this

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Nik was a pretty smart guy about 300

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years ago he came up with the first

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mathematical formulas to describe things

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in motion

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we couldn't have traveled up here into

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space without a good understanding of

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Newton's three laws of motion so what's

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the first law every material object

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continues in its state of rest or

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uniform motion in a straight line unless

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it is compelled to change that state by

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force is impressed upon it can we come

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up with a simpler way to say that an

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object at rest will remain at rest

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unless acted upon by an unbalanced force

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and an object in motion will remain in

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motion unless acted upon by an

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unbalanced force thanks professor aster

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that's much clearer you're welcome

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now for a demonstration here's the can

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of pudding

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it's at rest because it hasn't had any

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force applied to it so let's apply some

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force now our objects in motion and it

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will stay in motion at a constant speed

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in a straight line until it's acted on

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by an unbalanced force like a head don't

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try this at home

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now on to the second law it explains the

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relationship between course mass and

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acceleration force is a push or a pump

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acceleration is how fast an object

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changes its speed here's our can again

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we'll use this little air puffer to

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apply a gentle force to it for a short

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now we'll apply a greater force that did

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it it really accelerated that time the

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greater the force are greater the cans

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acceleration but how does mass come in

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the mass of an object affects how fast

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it will accelerate when a force is

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applied if you apply an equal amount of

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force to two objects the object with the

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most mass accelerates the least

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here are two cans of pudding tapioca and

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butterscotch if we apply the same force

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to both cans they should both accelerate

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the same and travel at the same rate of

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what happened one can seems to have

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wait here's the problem someone eats

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putting out of one of these cans without

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putting in the can the can has last

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class and thus it accelerates more

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Newton explained that force and mass are

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related to each other by acceleration a

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force is a push or a pull on the cam

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more force gives more acceleration mass

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resist acceleration if we gave the same

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push to two objects the one with less

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mass will accelerate more so here's our

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equation on top of the empty can and

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below the full force equals mass times

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acceleration so Newton wasn't wrong too

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late my pudding now what about Newton's

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third law of motion for every action

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there is an equal and opposite reaction

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well that's very easy to show up here in

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space what happens when Lacey pushes

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against Greg the force on each astronaut

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is equal and opposite so they go off in

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opposite directions at the same speed

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but once again mass plays a role in it

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all let's try that again but this time

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let's make it two against one the two

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crew members on the right have more maps

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together than our crew member on the

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left but the force is still equal when

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they push off of each other what do you

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think will happen now well you're right

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Lacey really goes sailing through the

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midday let's do that again this time in

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slow motion

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Lacey has less mass than the other two

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crew members Don and Greg and therefore

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he has a greater acceleration and

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travels faster let's run through these

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three laws of motion again an object at

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rest remain

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at rest unless acted upon by an

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unbalanced force and an object in motion

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will remain in motion at the same speed

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in the same direction unless acted upon

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by an unbalanced force the acceleration

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of an object depends upon its mass and

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for every action there is an equal and

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opposite reaction Newton's three laws of

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motion are not just formulas or words on