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Beginner's Guide
to Aerodynamics
Drag Equation  Level 1
Activity
 Click on The
Drag Equation to open the appropriate slide. Study the equation
and read the explanation of this concept. Then use the information
to complete the questions below.
 In the following
table, identify each variable in the equation. State the appropriate
units for each value :
Variable

Identity

English
Units

Metric
Units

D




Cd




r




V




A




A. What possible
reference areas(A) can be used to compute the drag?
B. If we want
to compute the L/D (lift to drag ratio), which reference area would
we want to use? Why?
C. Besides reference
area, air density and velocity, drag depends on several other values.
What variable is used to model many of the complex dependencies
of drag? What are some of the dependencies of drag incorporated
in this value?
 Calculate
the following problems which involve the Drag of an aircraft: (Before
computing, make sure all units agree.)
A. Suppose you
are flying an aircraft with the following wing shape and dimensions.
What is the total wing area?
B. The
thrust of the aircraft is 120,000 pounds and the air density is .00048
slugs/cu.ft. The current cruising speed is 450 ft/sec and we need to determine
the drag coefficient of the aircraft. Find the Cd. (Hint: you may want
to convert the original equation first)
C. Weather
conditions force the aircraft to descend to a level where the air density
is .00076 slugs/cu.ft. The engine thrust increases to 250,000 pounds.
At the new cruising altitude, what is the speed of the aircraft? (Hint:
once again, you may want to convert the equation first)
After landing,
the pilot switches aircraft. The new aircraft has a much different wing
shape and things get a little more complicated. If you are ready for
the challenge, try Drag Equation: Level
2.
HAVE FUN !!!!!

Related Pages:
Standards
Worksheet
Aerodynamics Activity Index
Aerodynamics Index


