Effect of propeller size on thrust produced
The hypothesis that increasing the propeller size will make the box move faster, is proven correct.
Propellers are part of a propulsion system that is used in marine ships and aircrafts. The rotating propeller creates a pressure difference between the rear and front blades that causes water or air to move from high pressure to low pressure areas. This produces a thrustforce of thrust that results in the motion of the aircraft or ship. Despite advances in technology, the propeller, which was invented in the early 1800s, remains the most widely used form of propulsion system in marine transport.
The science fair project can also be done by mounting the blades at different angles.
This experiment can also be repeated by changing the rotational speed of the motor.
Also consider - does the thickness of the propeller blade make a difference? What about the rigidity of the material used to make the propeller.
Propeller - http://en.wikipedia.org/wiki/Propeller
Aircraft propellers - http://www.thaitechnics.com/propeller/prop_intro.html
Ensure the blades are properly fixed to the wooden block so that they do not come loose when they rotate.