Part B? (2 Viewers)

[sicklad]

23 (b) the orbital velocity, what did you guys get and how?
and also for 29 (a)?

 

[Wight]

23 (b) the orbital velocity, what did you guys get and how?
and also for 29 (a)?

What was 29(a)...can't remember them at all.

 

[Fizzy_Cyst]

I think it was about 7692ms-1?

29(a) would be 2.26x10^15 photons

 

[Wight]

I think it was about 7692ms-1?

29(a) would be 2.26x10^15 photons

Fuck lol I miscalculated 29(a)...sigh

Can't use a calculator -.-

 

[weirdguy99]

I think it was about 7692ms-1?

29(a) would be 2.26x10^15 photons

That is correct.

 

[damo_g]

What was the method of working out the orbital velocity question. I can't remember my answer but if i see the method i will know if i got it right or not because i remember how i did it. I can hardly remember anything from part B.

 

[weirdguy99]

What was the method of working out the orbital velocity question. I can't remember my answer but if i see the method i will know if i got it right or not because i remember how i did it. I can hardly remember anything from part B.

The standard orbital velocity equation, v=ROOT(Gm/r).

You were given the Earth's radius and the altitude of the satellite, and since you know G, then solve for V.

 

[damo_g]

The standard orbital velocity equation, v=ROOT(Gm/r).

You were given the Earth's radius and the altitude of the satellite, and since you know G, then solve for V.

I think i found what the period was by r^3/T^2 = GM/4pi^2 and then solved v with V = 2rpi/t Is this wrong because i assumed its orbit as a circle? I think i overcomplicated this one, easy marks lost if i did.

 

[weirdguy99]

I think i found what the period was by r^3/T^2 = GM/4pi^2 and then solved v with V = 2rpi/t Is this wrong because i assumed its orbit as a circle? I think i overcomplicated this one, easy marks lost if i did.

You always assume it's a circle since all of the equations contain the radius. v=[2(pi)r]/T probably would have worked. I think the values were 350KM altitude, 6730KM Earth radius and 5.97x10^24kg Earth mass. Try both methods and if you get the same answer, you can probably expect full marks. Although, the marker would probably be shaking his/her head

 

[damo_g]

You always assume it's a circle since all of the equations contain the radius. v=[2(pi)r]/T probably would have worked. I think the values were 350KM altitude, 6730KM Earth radius and 5.97x10^24kg Earth mass. Try both methods and if you get the same answer, you can probably expect full marks. Although, the marker would probably be shaking his/her head

yep it got the right answer. Silly of me going the long way round though hah. I'm just relieved i didn't lose a couple easy marks.

 

[weirdguy99]

yep it got the right answer. Silly of me going the long way round though hah. I'm just relieved i didn't lose a couple easy marks.

Goodie

 

[Entity]

Dammit i forgot the radius of the earth

 

[Username2]

Dammit i forgot the radius of the earth

Do you reckon that'll be minus 1/2/3 ?

 

[weirdguy99]

Do you reckon that'll be minus 1/2/3 ?

I guess -1 mark?

 

[cro4lyf]

Could some tell me if what I did was right..

I made F=mv2/r and F=ma become mv2/r=ma, then I found the value of a at the height of the rocket (a=g) using g=Gm/r2 which gave me an answer of around 8.7... I then rearraged the formula and eventual got to v=ROOTar.. Got an answer somewhere in the seven thousands, not sure of the exact value, but I have a feeling I probably fluked it.. Could someone please tell me if what I did could get me any marks ?

 

[damo_g]

Could some tell me if what I did was right..

I made F=mv2/r and F=ma become mv2/r=ma, then I found the value of a at the height of the rocket (a=g) using g=Gm/r2 which gave me an answer of around 8.7... I then rearraged the formula and eventual got to v=ROOTar.. Got an answer somewhere in the seven thousands, not sure of the exact value, but I have a feeling I probably fluked it.. Could someone please tell me if what I did could get me any marks ?

The answer was 7692m/s. Someone put up what the radius and mass was earlier in this thread. Find the values in this thread and go back through the method and see if you got the right answer. If you got the right answer then i don't see why you wouldn't get full marks.

 

[LeightonChops]

i got about 7000m/s, using the GM/4piesquared = r^3 / T^2 and v = 2pieR/T method. Your method works i think as well

 

[damo_g]

i got about 7000m/s, using the GM/4piesquared = r^3 / T^2 and v = 2pieR/T method. Your method works i think as well

I used this as well and got the right answer. The answer was posted earlier in the thread, it was somewhere in the 7000s.

 

[Screamm]

The answer was 7692m/s. Someone put up what the radius and mass was earlier in this thread. Find the values in this thread and go back through the method and see if you got the right answer. If you got the right answer then i don't see why you wouldn't get full marks.

i got this aswell..

 

[utanobeiiby]

I think it was about 7692ms-1?

29(a) would be 2.26x10^15 photons

yeah i got this too xD but i was being careful with the significant figures and stuff cause considering this paper being too easy>.. markers can be mean and mark on significant figures