Using Graphs to Compare Lift Variables Answers

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 Data Table

Variable	Description	Explanation
Angle of attack	A straight line at less than a 45o angle through 0,0. The lift and angle show + and - numbers.	The straight line shows a steady increase. If you double the angle, then you double the lift.
Thickness of airfoil	A slight upward curve.	The curve shows that as the thickness increases the lift also increases, but to a lesser degree.
	At angle = 0.0, there is no line on the graph.	For a symmetric airfoil, a change in thickness will not change the lift.
Camber	A straight line at less than a 45o angle through 0,0 with lift being both + and -.	The straight line shows a steady increase.
Airspeed	An upward curve where the slope of the line increases with increased speed.	The upward curve shows that lift increases at a greater rate than the speed increases.
	At angle = 0.0, there is no line.	For a symmetric airfoil, a change in airspeed does not create lift.
Altitude (density)	A downward curving line where the slope decreases with altitude.	As altitude increases the lift that results decreases; but the decrease lessens with altitude. ( As the altitude increases, the density of the air decreases. So lift decreases as density decreases.)
Area of airfoil surface	A straight line at a 45o angle through 0,0.	The lift increases at the same rate as the area.

Questions

1. What does a graph with a straight line tell us about how the data changes? A graph with a straight line shows a steady increase (or decrease depending on the slope).
   
2. What does an upward curve indicate on a graph? A graph with an upward curve has an increasing slope. So as the independent variable increases, the dependent variable increases, but at a greater rate.
   
3. How does the data change if you have a line that curves downward on your graph? A downward curve shows a decrease at a varying rate.
   
4. Which lift variables seem to change at a steady rate? Angle, camber, and area seem to increase at a steady rate.
   
5. Which lift variables tend to change at an increasing rate? Decreasing rate? Airspeed increases at an increasing rate. Altitude decreases at a decreasing rate, while thickness increases at a decreasing rate.