Activity #2:

Graphing the Four Forces

 

Background: The concept of force can be effectively represented on a graph using the Cartesian coordinate system. By representing four of the aeronautical forces (lift, drag, ,thrust ,weight) on a graph, students can visualize both parts of the definition of force:magnitude and direction. This lesson concentrates on the actual representation of the four forces on a graph. If, after combining the four forces, the net force is plotted in the upper right quadrant of the graph,then we will draw the conclusion that the airplane is able to fly.

 

Directions: Have students examine the graph on the following page. Point out that lift is "up toward the top of the paper", weight is "down toward the bottom of the paper", thrust is "forward toward the right of the paper" and drag is "back toward the left of the paper".
 
Using the magnitudes below,follow the steps and plot your points on the graph on the previous page.
 
Weight 3 units
Lift 7 units
Drag 2 units
Thrust 5 units
 
 
The forces can be plotted in any order.For example:
 
Step 1:Start at the origin (center of graph)and count down three squares (for Weight).Plot a small dot.
 
Step 2:From that small dot (do not start again from the origin!)count up seven squares (for Lift).Plot another small dot.
 
Step 3:From that small dot (do not start again from the origin!)count to the left two squares (for Drag).Plot another dot.
 
Step 4:From that small dot (do not start again from the origin!)count to the right 5 squares (for Thrust).Plot a large dot.This is the representation of the net force. See the graphs on the page 9 for guidance,then continue.

a graph with x representing drag to thrust and y representing weight to lift

four graphs, the first is labled step one, down 3 an arrow from the xy intersection points to a dot at -3, the second graph is labled step 2: up 7 an arrow beginning at -3 on the y axis points to a dot at 4, the third graph is labeled Step 3: Left 2 an ar

Step 5:Determine whether or not the airplane is flyable. If the net force is plotted in the upper right quadrant,the airplane is flyable. If the net force is plotted in the upper left quadrant,the airplane is not flyable -it has too much drag. If the net force is plotted in the lower left quadrant,the airplane is not flyable -it has too much drag and weight. If the net force is plotted in the lower right quadrant,the airplane is not flyable - it has too much weight.

graph

Exercise 1

Exercise 2