Chaoter 18 Grav Fields

Question 1

What is escape velociy full definition

Answer 1

The velocity required for a body to escape the gravatioanl FIELD of a mass with no FURTHER ENERGY INPUT

Question 2

So what 2 reasons is there thst a spaceship does not need to ACHIEVE THE escape velocity to get to their orbit

(Think does it need to escape?)

Answer 2

1) Not all the energy provided by escape velocity is needed straight away, a continous thrust can be provided by the fuel as it rises

2) foes not need to ESCAPE THE EARTHS grav field to get into orbit, in fact without the pull it wouldn’t be able to orbit

Question 3

Why will acc velocity need to be greater?
(Think about three assumptions)

Answer 3

All the ke is transferred, not gonna happen in reality

Question 4

Remember 2 other conditions needed for geostationary are actually tested on what are they?

So basically why can a satellite never exist in top of a pole

Answer 4

Must be equatorial orbit

Must rotate in shame direction as planet (if it’d on pole, it will never rotate in the same direction )

Question 5

How to answer why binary stars must be diametrically opposite AT ALL TIMES for them to both krbits

Question 6

Always try to find answer without usign CALCUAKTED values

So for example for v should’ve done

Answer 6

Should do v = wr instead of equations grav force to centripetal

Question 7

Why when using binary star systems and deriving Keplers law, what to do with radii?

General case of say earth orbiting moon

Answer 7

Centripetal force = gravational force as the gravity force provides for the centripetal force

Now rhe centripetal force always acts to the CENTRE OF ROTATION, and grav force is between rhe radii or both the masses.

Now in general case, with earth and moon, the centre of mass is SO CLOSE to the earth, that the centre of rotation is basically the centre of the earth. In this case, we use the centre of the earth to be the direction of ROTATION and the distance for grav, so same r is there

But when the stars are of SIMILAR MASS, the centr of rotation si not the same as one of the stars centre . Thus for the centripetal you take one distance, but for grav force always must go from centre to centre!

Question 8

What’s a stipulation about the binary star system for time period and WHY

Answer 8

they must be the same , objectively looking if they are always opposite then they will be.

However also