Weight force and jupiter (1 Viewer)

[velox]

Ah ok, those type of questions were in marsdens notes, thats why they were all positive. So do u think they are comprehensive enough?

 

[helper]

Ah ok, those type of questions were in marsdens notes, thats why they were all positive. So do u think they are comprehensive enough?

I haven't looked at the questions in Marsden book for a while so can't comment.

I would say as long as you can do calculations with the formula your right for the second point.

This is what they probably expect for a multiple choice question or a short response as a longer part question.

For a longer mark question you would need to:

For the first you should be able to quote the work formula, and explain changes in PE in terms of that.

W=Fd

For an object moving away from the surface of the Earth work is being done on the object agianst the gravitational field so it is gaining GPE. Being able to substitute Newtons equation into this to come up with E, and why it is negative.

 

[velox]

Cool, yeah the sheet i just did covered most of it pretty well. Thank again!

 

[clonestar]

How can an object have a negative gpe, if gpe is the like, the higher the object the more gpe it has, and the lcloser it is to the mass, the less gpe it has.

The potential energy is a property of the system of two particles not one.

There is no way to divide this energy.

Take for example a baseball and the earth as m1 and m2 and the baseball is way out in space(infintely) away from earth.

As it is with nothing moving the potential energy of the system is zero.

However as the baseball now approaches the earth the Potential energy is negative of the work done due to OPPOSITE direction.

i.e. gain in kinetic energy = loss of potential energy.... <-hence the negative sign. going below zero.

Does that analogy help at all?


Also just a bit more as PE=- Gm1m2/r as r increases PE decreases, approaching zero(ASSUME + DIRECTION). Therefore if r decreases the potential energy is now in the opposite direction hence the (- symbol)




CLoNEStar

 

[velox]

yep, got it now. thanks guys

 

[clonestar]

Ah ok, those type of questions were in marsdens notes, thats why they were all positive. So do u think they are comprehensive enough?

I use these notes(marsden) with my students.

They certainly are not the complete of Year 12 Physics thats for sure but that are ok for students notes etc.

I use Giancoli Physics principles with applications for any concepts that are poorly writen in the Marsden notes i.e. the Gravitational force section and the potential energy section.

Also the jacaranda book looks very good as well and my students have this book as well.


ClONEStAr

 

[velox]

Yeah im going to use the marsden notes, jacaranda, physics contexts and the macmillian book, probably in conjunction with excel maybe.

Sorry i have another question that i wasn't so sure on.

If you were to place a graph of the E_P around Jupiter next to the graph shown for Earth, how would the two graphs differ?

 

[clonestar]

If you were to place a graph of the E_P around Jupiter next to the graph shown for Earth, how would the two graphs differ?

Based on the fact that the mass of Jupiter is enormous compared to earth and that E(potential) is proportional to the mass of the planet i.e. jupiter you would have to say that the graph for jupiter would be much larger in terms of potential energy compared to earth assuming r is constant in both.


if you were plotting a graph of PE Vs r

it would look like a hyperbola with asymptotic relationship.

Enjoy

CloNESTER