Flight Instructor________________________
4.2.02 Changing Forces of Flight
Amelia Earhart, a pioneer in aviation, was the first woman
to fly across the Atlantic Ocean by herself in 1932.
However, like all pilots, she too had to learn the physics of
flight. She had her first flying lesson on January 3, 1921,
when she was 23 years old.
Let’s pretend that you are her flight instructor, starting
with a lesson on the four forces and how they affect flight.
1. Label the four forces of
flight on the image to the
right. Then turn to Amelia
(your partner) and explain
what creates each force.
Take turns being the flight
instructor!
2. The forces on the plane above are ______________________________ .
3. This means that the plane moves at a ________________________________ in a straight ____________ .
4. To change the velocity (direction, altitude, and/or speed), the forces must be ______________________ .
5. For each scenario, identify the force(s) that change(s), indicate whether it increases (I) or decreases (D),
and describe the resulting change in motion of the plane. Be sure to check with Amelia that she
understands each flight situation!
Scenario
Changing
force(s)
I or D?
A plane is sitting still on the
runway. The pilot turns on the
engine and the plane moves
forward.
The plane continues to
accelerate on the runway to the
point where the plane leaves
the ground.
1
Result
Scenario
Changing
force(s)
I or D?
A plane is flying at a constant
speed in a straight line through
the air, but suddenly the engine
stops working.
A plane is flying at a constant
speed in a straight line through
the air. All of the sudden the
plane flies through an air pocket
(a localized region of low air
density or a descending air
current).
A fire-fighting plane is flying
over the forest fire and dropping
1000 gallons of water on the
fire.
A skydiver jumps out of a plane,
but while doing so, his
parachute deploys and gets
caught on the plane, leaving the
skydiver and the parachute
dangling below the plane.
A plane is flying at a constant
speed in a straight line through
the air, when the pilot increases
the engine output.
A plane is flying at a constant
speed in a straight line through
the air, when both the wings fall
off. (Yikes!)
A glider is flying at a constant
speed in a straight line through
the air when it experiences a
sudden updraft.
An advertisement plane with a
banner is flying at a constant
speed in a straight line through
the air, when it all of the sudden
loses its banner.
2
Result
Next, let’s show Amelia how to calculate the force that acts on an airplane that is flying in the air. All forces
acting on a plane are measured in Newtons. In order to calculate the total force acting on a plane we have to
determine the NET FORCE.
Forces that act in the same direction are added, while forces that act in opposite directions are subtracted. On
airplanes there are always two sets of forces that act in opposite directions.
NET FORCE
Horizontal:
50,000 N
20,000 N – 18,000 N = 2,000 N Right
18,000 N
20,000 N
Vertical:
50,000 N – 50,000 N = 0 N
50,000 N
Result?
Plane accelerates (speeds up)
NET FORCE
Horizontal:
60,000 N
20,000 N
20,000 N
Vertical:
Result?
50,000 N
_______________________________
NET FORCE
Horizontal:
40,000 N
Vertical:
20,000 N
20,000 N
Result:
50,000 N
_______________________________
3
NET FORCE
Horizontal:
50,000 N
22,000 N
20,000 N
Vertical:
Result?
50,000 N
_______________________________
NET FORCE
Horizontal:
50,000 N
20,000 N
20,000 N
Vertical:
Result?
50,000 N
_______________________________
NET FORCE
Horizontal:
53,000 N
20,000 N
23,000 N
Vertical:
Result?
50,000 N
_______________________________
Thank you for explaining the four forces of flight and clarifying each flight situation to Amelia.
She became an excellent pilot, setting many aviation records. In 1937, she set out on her
second attempt to fly around the world. After completing 22,000 miles, she and her partner
started on the last leg of 7,000 miles across the Pacific Ocean. Tragically, they never arrived at
their final destination and went missing on July 2, 1937.
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