- #1
Blem
- 2
- 0
Alright guys, just looking for a point in the right direction for a tutorial question.
GIVEN VALUES:
Temperature change with increasing altitude: 0.0065 K/m
Temp at sea level: 15ºC
Pressure at sea level: 101.5 kPa
FIND:
Atmospheric pressure at 7500m.
So what I've done is found the temperature decrease between sea level and 7500m, so that temperature is 239.4K.
And then tried (P1/T1)=(P2/T2), was a bit sceptical over this working.. it didn't.
After that tried:
∫(1/P) dP = -∫(g/RT) dz
Integrated that, giving:
ln(P2/P1) = (-g/RT)(z2-z1)
Placed in the values given/calculated, leading to:
P = 101500*e^[(-9.81*7500)/(287*288.15)]
P = 41.7 kPa
... which is a wee bit off the stated answer of 38.3 kPa.
Any ideas?
GIVEN VALUES:
Temperature change with increasing altitude: 0.0065 K/m
Temp at sea level: 15ºC
Pressure at sea level: 101.5 kPa
FIND:
Atmospheric pressure at 7500m.
So what I've done is found the temperature decrease between sea level and 7500m, so that temperature is 239.4K.
And then tried (P1/T1)=(P2/T2), was a bit sceptical over this working.. it didn't.
After that tried:
∫(1/P) dP = -∫(g/RT) dz
Integrated that, giving:
ln(P2/P1) = (-g/RT)(z2-z1)
Placed in the values given/calculated, leading to:
P = 101500*e^[(-9.81*7500)/(287*288.15)]
P = 41.7 kPa
... which is a wee bit off the stated answer of 38.3 kPa.
Any ideas?