The rocket launch and changing gravity

[marco12345a]

When a rocket is launched, it starts not with velocity zero, but with the rotation velocity which the Earth gives it. Thus if a rocket is launched eastward, it requires a smaller boost (and if westward, a larger one) to achieve orbit. with a latitude of 31.1 degrees, cos(31degrees) 24902/24 = 393.11 ms/s

To escape velocity on Earth = (2G Mearth / r earth) = 11200ms-1
So the total velocity that needed for the rocket = 11200 - 393.11= 10806.99ms-1

I am trying to find the total energy that is needed for the rocket of 1000kg to escape velocity

i used the question
m = 1000 x 9.8 N

E= 1/2 m^2
= 5.84 X 10^10 J

my question is : as the further you are away from earth, there will be less gravity. So if i use that equation, would that be accurate assume there is no air friction and the mass of the rocket doesn't change due to the loss of fuel

 

[PhysicoRaj]

That would be close enough! But the problem is that the accuracy falls as u go on neglecting decreasing mass due to consumption of fuel.

 

[marco12345a]

should i use the equation of E= 1/2 m^2 ?

 

[PhysicoRaj]

should i use the equation of E= 1/2 m^2 ?

If u r calculating energy, then of course it'll do. note that, E=1/2mv^2=GMm/r

 

[marco12345a]

but doesn't the changing gravity affect the m ?

 

[PhysicoRaj]

but doesn't the changing gravity affect the m ?

Yes but if u really want to solve it u will hav to take an average of that.

 

[PhysicoRaj]

but doesn't the changing gravity affect the m ?

more than that...changing mass is a prob.

 

[marco12345a]

for example if a rocket is 1000 kg on Earth , what would the gravity be when it is at 300m

 

[PhysicoRaj]

for example if a rocket is 1000 kg on Earth , what would the gravity be when it is at 300m

If u r dealing with mass, it would be 1000Kg itself. if u r dealing about wight, itll bcom
W=mg
=1000*g
g= gravitational acceleration at 300mts
u manipulate it...
g=w/m
=w/1000
ul hav to know its weight there.

 

[marco12345a]

how do you find the changing gravity ?

 

[PhysicoRaj]

i need to go offline. sorry. u can mail me at nrajathb96@gmail.com il answer from there.

 

[PhysicoRaj]

the gravity doesn't change preferentially at 300mts
observ: g=9.806 in 0mts
g=9.803at 1000mts

ok bye..

 

[marco12345a]

okay thank you very much