Aerodynamics/Physics Help

OUTTIE

OUTTIE

Well-Known Member
I need help answering a physics question.

Given: An indicated airspeed of 248 mph at standard sea level conditions (density of 0.00238 slugs/ft³). Assuming that there are no instrument, position, or compressibility errors, what would be the indicated airspeed at an altitude of 25,000 feet and a density of 0.00107 slugs/ft³ with the same dynamic pressure?

a. 248 mph
b. 542 mph
c. 370 mph

Given the same conditions as above what would be the true airspeed at 25,000 feet?

a. 248 mph
b. 542 mph
c. 370 mph

A straight wing with a critical Mach number of 0.78 is swept to an angle of 37 degrees. How fast may the airplane be flown without exceeding the critical Mach number?

a. .88
b. .93
c. .98
d..83

thanks!
 
I would love to help you out of these but I left my aerodynamics notes at home. I know for the first two there is a simple formula you can plug it into! When I get back home on Wednesday, if its not to late I will try and find my old college notes and give it to you.
 
OUTTIE said:
I need help answering a physics question.

Given: An indicated airspeed of 248 mph at standard sea level conditions (density of 0.00238 slugs/ft³). Assuming that there are no instrument, position, or compressibility errors, what would be the indicated airspeed at an altitude of 25,000 feet and a density of 0.00107 slugs/ft³ with the same dynamic pressure?

a. 248 mph
b. 542 mph
c. 370 mph
Click to expand...

Sneaky question. a.

Given the same conditions as above what would be the true airspeed at 25,000 feet?

a. 248 mph
b. 542 mph
c. 370 mph
Click to expand...
248* sqrt(.00238/.00107)
= 369.8 = 370 mph

A straight wing with a critical Mach number of 0.78 is swept to an angle of 37 degrees. How fast may the airplane be flown without exceeding the critical Mach number?

a. .88
b. .93
c. .98
d..83

thanks!
Click to expand...
.78/cos(37) = .976 = .98
 
OUTTIE said:
I need help answering a physics question.

Given: An indicated airspeed of 248 mph at standard sea level conditions (density of 0.00238 slugs/ft³). Assuming that there are no instrument, position, or compressibility errors, what would be the indicated airspeed at an altitude of 25,000 feet and a density of 0.00107 slugs/ft³ with the same dynamic pressure?

a. 248 mph
b. 542 mph
c. 370 mph

Given the same conditions as above what would be the true airspeed at 25,000 feet?

a. 248 mph
b. 542 mph
c. 370 mph

A straight wing with a critical Mach number of 0.78 is swept to an angle of 37 degrees. How fast may the airplane be flown without exceeding the critical Mach number?

a. .88
b. .93
c. .98
d..83

thanks!
Click to expand...

Dynamic press = IAS. As previous poster said, tricky question.
 
z987k said:
just curious, where'd you get this equation from?.. or rather what is the equation called/etc. I assume those are constants?
Click to expand...

The numbers are the air densities at the respective altitudes. You can derive the relation from the lift equation or just set the two dynamic pressures equal to each other and solve for the TAS at altitude.
 
Pilotforhire587 said:
I would love to help you out of these but I left my aerodynamics notes at home. I know for the first two there is a simple formula you can plug it into! When I get back home on Wednesday, if its not to late I will try and find my old college notes and give it to you.
Click to expand...

thanks but I think grayson beat ya :P

wow thanks guys! you just made me understand it more. That one question is really hard for me to figure it out and I know the formulas but was just confused. I had a list of formulas to look at but ain't sure which one to use..

Grayson, you made me feel dumb haha I had trouble calculating the mph instead I left out the square root...no wonder I got these weird numbers.

So yah, my teacher just put 8 of these on the wboard for hw.
 
OUTTIE said:
dumb haha I had trouble calculating the mph instead I left out the square root...no wonder I got these weird numbers.
Click to expand...

You have to remember that mathematics is purely subjective and no one way of manipulating the numbers is more correct than another. The fact that my numbers conform to empirical evidence is absolutely meaningless, because there are many truths which are unverifiable in physical reality.

So you should really just turn in your original numbers and explain to your teacher that these numbers are just as good as anyone else's and that it's only his ethnocentric dogma that makes him think that one form of truth is superior to another.
 
tgrayson said:
You have to remember that mathematics is purely subjective and no one way of manipulating the numbers is more correct than another. The fact that my numbers conform to empirical evidence is absolutely meaningless, because there are many truths which are unverifiable in physical reality.

So you should really just turn in your original numbers and explain to your teacher that these numbers are just as good as anyone else's and that it's only his ethnocentric dogma that makes him think that one form of truth is superior to another.
Click to expand...

lmao! wrong thread.
 
tgrayson said:
You have to remember that mathematics is purely subjective and no one way of manipulating the numbers is more correct than another. The fact that my numbers conform to empirical evidence is absolutely meaningless, because there are many truths which are unverifiable in physical reality.

So you should really just turn in your original numbers and explain to your teacher that these numbers are just as good as anyone else's and that it's only his ethnocentric dogma that makes him think that one form of truth is superior to another.
Click to expand...

This post made my day. :)
 
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