# 4. PROPELLER THRUST DEMO

from Come Fly With Me – Exploring Science through aviation and aerospace concepts.

SUBJECT: Science
GROUP SIZE: Large
TIME: 45 minutes
TYPE OF ACTIVITY: Teacher Demonstration Student Investigation
TEACHING STRATEGY: Guided Discovery
CONCEPTS: Propeller Pitch, Newton’s 3rd Law, Thrust
SKILLS: Observation, Inference, Hypothesizing

Objectives: To investigate how a propeller produces thrust and the results of that thrust; to relate the results of this investigation to Newton’s Third Law of Motion.

Materials: 6 or more round pencils or pieces of doweling; a flat board; an electric fan and extension cord; model airplane propellers.
SAFETY NOTE: DO NOT ALLOW THE STUDENTS TO INVESTIGATE THE PITCH OF THE PROPELLER WHILE THE FAN IS PLUGGED IN!
Procedure:

1. Have the students examine the propellers and the blades of the fan. Have them hypothesize as to the direction of thrust based on the direction of rotation.
2. Have them rotate the blades slowly to see what action they may have on the air.
3. Place the board on several pencils which have been placed parallel to one another on a hard flat surface. Place the fan on the board and plug it in.
4. Have the students observe the resulting action/ reaction and feel the thrust of air from the propeller in the fan.
5. Have them then apply this information to their hypotheses and explain which direction thrust will be produced by the model airplane propellers.

Extension: Have the students actually make a propeller out of wood. Have them investigate the effect of pitch (angle of attack) of different propellers. Relate this experiment to the one on rocket nozzles which dealt with velocity as a result of pressure. Relate the propeller concept to a boomerang.

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