Getting wrong answer,

So I have these formula's and information given to me. From question 1 I find the Zi values which I have done using Sym Z and solve, I found what B was no problem (I dont have what Go and Rs are in the pictures but it's in my script.) I am also given the first Pi values which is 101325, from that I put it into the equation and get what P(2) is. However my script is outputting me very different numbers to the answers of Pi in equation 5 and I cant figure out why.

Any help is appreciated!

Answer 1

[Sulaymon Eshkabilov]

Hi,

In your code, there are a few errors with loop indexes. Here is the fixed part of the script that gives all correct answers:

...
    
Pa=Pi; HH=diff(hi);  TT=Ti; AA=Ai_1;  % New variables are introduced not to get confused with the variable names containing i :). This is optional though!

for i= 1:length(ai)
    if AA(i) ==0  
       Pa(i+1)= real(Pa(i).*exp(-B*HH(i)/TT(i)));  % Pressure values are saved
    else Pa(i+1)=real(Pa(i)*(TT(i)/(TT(i)+ai(i)*HH(i))).^(B/AA(i)));  % Pressure values are saved 
    end
end     

[Liam Crocker]

Just a little confused as to why HH = diff (hi)

If you have Real in there, wouldn't that mean you are getting complex numbers which means im getting the wrong answer

[Sulaymon Eshkabilov]

diff(hi) is equivalent of hi(i+1)-hi(i)

Pa() values are all REAL not complex and real() not needed (was left unintentionally).

...
    
Pa=Pi; HH=diff(hi);  TT=Ti; AA=Ai_1;  % New variables are introduced not to get confused with the variable names containing i :). This is optional though!

for i= 1:length(ai)
    if AA(i) ==0  
       Pa(i+1)= (Pa(i).*exp(-B*HH(i)/TT(i)));  % Pressure values are saved
    else Pa(i+1)=(Pa(i)*(TT(i)/(TT(i)+ai(i)*HH(i))).^(B/AA(i)));  % Pressure values are saved 
    end
end     

[Liam Crocker]

Ah! Makes sense!

[Sulaymon Eshkabilov]

Would you accept the answer? Cheers :)

[Liam Crocker]

Yes of course! My apologies!

[Liam Crocker]

Hi Sulaymon,

When I call Pa(6), it returns me a very close value, but not the same as what's listen on the fprintf table below. Pa(6) for me returns 66.9464 where it is 66.9388 on the table, do you have any idea why?

[Sulaymon Eshkabilov]

Mostly, because of the value (gravitational acceleration):

go = 9.80666