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23 Apr 2018, 00:29
Kudos
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
72% (01:38) correct
28%
(02:34)
wrong
based on 56
sessions
History
Date
Time
Result
Not Attempted Yet
The formula for lift, the force that holds an airplane in the air, is \(L = C_L(\frac{dAV^2}{2})\). When d is measured in pounds per cubic feet, A is measured in square feet, V is measured in feet per second, and if \(C_L\) is a numerical coefficient with no units attached, what are the units for the lift of an airplane?
(A) \(\frac{lb*ft}{sec^2}\)
(B) \(\frac{lb}{sec^2}\)
(C) \(\frac{lb*ft}{sec}\)
(D) \(\frac{lb*ft^2}{sec^2}\)
(E) \(\frac{lb^2*ft^2}{sec^2}\)
(A) \(\frac{lb*ft}{sec^2}\)
(B) \(\frac{lb}{sec^2}\)
(C) \(\frac{lb*ft}{sec}\)
(D) \(\frac{lb*ft^2}{sec^2}\)
(E) \(\frac{lb^2*ft^2}{sec^2}\)
23 Apr 2018, 00:47
Kudos
Bookmarks
Bunuel
As we're asked to do a straightforward calculation, we'll just do it without thinking too much.
This is a Precise approach.
We'll substitute the various values into our given expression writing (feet)^3 instead of cubic feet, (feet)^2 instead of square feet and ignoring our constants (as they have no units).
\(\frac{pounds}{feet^3}\cdot (feet)^2 \cdot (\frac{feet}{second})^2=\frac{feet\cdot pounds}{second^2}\)
Then (A) is our answer.
