Newton and escape velocity (1 Viewer)

[velox]

Outline Newton’s concept of escape velocity
For this dot point do we just need to talk about what the concept behind what he did was, or what he did aswell (i.e detail his cannon process) ?

 

[KFunk]

As the dot point suggests I think it's more about his concept. Rather than considering the initial velocity required to escape Earth's gravitational field I think he was considering the velocity of projection that would send an object into orbit.

 

[velox]

yeah so the dot point is a little screwed.

 

[m111]

Be wary not to oversimplify any dps for your subjects... it is not widely known, but the Dept of Ed reserves the right to ask "higher order verb" questions in the HSC even on "lower order" dps!!!

 

[...]

just learn everything about it, i mean its not that much to learn

 

[velox]

yeah i wrote down the whole process. I was just trying to cut the dot point summaries length.

EDIT: Cos i looked at Timmy's summary and some of his dot point answers are very short.

 

[zenger69]

According to my physics teacher.

Outline Newton's Concept of Escape Velocity: (if they give you that question in the HSC you would have to answer something like)

Newton's concept of escape velocity was someone on top of a mountain firing a canon. The greater the initial velocity the greater the range the canon ball fired. Newton proposed that at a greater velocity the canon ball would go into orbital velocity and at an even greater velocity, the canon ball would escape the gravitational attraction of Earth therefore reaching escape velocity.

Also drawing a diagram of the Earth and paths of the different projectiles.

And this would earn you 5 marks.

oh and did you know the moon is falling. (it sounds ludicrous but i read somewhere that its true) because it's on Orbital velocity.

 

[Stan..]

oh and did you know the moon is falling. (it sounds ludicrous but i read somewhere that its true) because it's on Orbital velocity.

I think it is the other way around. It is moving away.

 

[zenger69]

well teacher kept saying it was falling towards earth.

except I argued it was moving at a tangent away from the earth.

But well.... it's doing both thats why it's rotating the earth in a circular motion. It's the addition of two vectors.

I said it to see if anyone else had any good arguments to say whether it's falling.

 

[Ghost1788]

Apparently the moon is moving away from the earth at a rate of 1cm per year that is its average orbital distance/radius is increasing my 1 cm year.....

At that rate during a life time of 100 years it has moved 1m

IF this is true i guess this rate of increasing radis("radius") will increase though it will take a while for an siginifcant change to occur as 1m doesnt really diminish the effect of gravity on the moon from the earth by alot now does it...

 

[zenger69]

ok cool... do you have proof or some sort of article i can print out and bring to my teacher?

 

[velox]

Some Credible Sources:
http://teacher.scholastic.com/researchtools/articlearchives/space/moon.htm
http://www.newscientist.com/backpage.ns?id=lw774

 

[zenger69]

but it doesn't make sense to me.

Because the earth is so much bigger than the moon, therefore it's logical that gravitational attraction is much greater. So it should be falling but it's velocity equals that force making it move in a circle.

So how it moves away surprises me.

 

[krabby_me]

Falling?

Ok. I didnt understand that the earth was falling until a few weeks ago. I read a physics book and it explained it to me clearly and logically. I cant remember which one it was though. Ill try to explain it as best as i can.

The earth is orbiting the sun. The earth is also rotating on its axis, and the moon is rotating around the earth.

As the earth is orbiting, the moon is continuously falling down behind the earth. And thats why it is falling towards the earth.

An astronaut floats because the satellite is falling. They are falling at the same rate, and so the satellite never overtakes the astronaut.

I probably confused you all, but if i find the book that it explained it to me ill post it.

 

[velox]

Ermm, isn't is that the Moon is falling away, not the Earth?

 

[Ghost1788]

srry i read about the moon moving away a long time ago so i cant remember where or even when i read it though the reason for it would be that the centripetal force of the moon(the force experienced by any object moving in a circular motion) is greater than that of the force or acceleration due to gravity thus the moon would move away from earth at ever a slow pace. I guess that the moons orbital velocity of the earth is just greater than the escape velocity required.....

Because the earth is so much bigger than the moon, therefore it's logical that gravitational attraction is much greater. So it should be falling but it's velocity equals that force making it move in a circle.

Remember that inverse square law applies to gravity

Ermm, isn't is that the Moon is falling away, not the Earth?

Its all realative.....
the moon orbits the earth, the earth orbits the sun, the sun 'orbits the large body which is in the centre of the milky way galaxy and i wouldnt be suprised if the milkyway galaxy orbited another massive body......'

( ' ' = Not too sure but my guess)


Ghost1788

 

[kylemac96]

I think it is the other way around. It is moving away.

The moon is falling into the earth. However, the velocity the moon has tangential to the gravitational acceleration is at an equilibrium (well almost), therefore the moon falls around the earth in a slightly elliptical orbit. BTW, the moon is still moving away from the earth... but thats a different story.