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How do car propellers work?

Published in Rubber band cars 2 mins read

Car propellers, particularly in simple toy models, work by using stored energy to spin blades that push against the air, creating thrust that propels the car forward.

Understanding Propeller Power

In many basic car propeller designs, the power source isn't a complex engine but a simple, effective mechanism: the rubber band.

The Role of the Rubber Band

The process starts when you manually interact with the propeller.

"When you wind up the propeller, you are storing energy in the rubber band that is released when you let the car go." This stored energy is potential energy, specifically elastic potential energy held within the stretched or twisted rubber band.

Energy Release and Propulsion

When you release the propeller, the rubber band rapidly returns to its original state. As it unwinds, it causes the connected shaft and propeller blades to spin very quickly.

The spinning propeller blades are shaped to push air backward. According to Newton's Third Law of Motion (for every action, there is an equal and opposite reaction), pushing air backward results in a forward force on the propeller and, consequently, on the car it's attached to. This forward force is known as thrust, and it's what makes the car move.

Factors Affecting Performance

The amount of energy stored dictates how much thrust is generated and for how long.

  • Winding: "The more times you wind the propeller, the more energy you store and therefore, the further the car should go." More stored energy means the rubber band unwinds with greater force and spins the propeller faster or for a longer duration, leading to more thrust and a longer travel distance.
  • Propeller Design: The size, shape, and number of blades on the propeller also affect how efficiently it converts rotational energy into thrust.
  • Car Design: Factors like the car's weight, wheel friction, and aerodynamics influence how effectively the thrust moves the vehicle.

Essentially, winding stores potential energy in the rubber band, releasing it converts this to kinetic energy spinning the propeller, and the spinning propeller converts this rotational energy into linear thrust by pushing air.