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# Rubber Band Powered Airplanes - PowerPoint PPT Presentation

Rubber Band Powered Airplanes. By Angela Coburn University of British Columbia Department of Physics and Astronomy. Outline. History of Rubber Powered Aircraft Newton’s Second and Third Law’s Four Forces Acting on an Airplane Energy, Work and Power Transport Cost Calculations

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Presentation Transcript

By Angela Coburn

University of British Columbia Department of Physics and Astronomy

• History of Rubber Powered Aircraft

• Newton’s Second and Third Law’s

• Four Forces Acting on an Airplane

• Energy, Work and Power

• Transport Cost

• Calculations

• Building Airplanes

• Summary

• 1903 – Wright brothers made the first human flight.

• As children they received a rubber powered toy helicopter.

• When they broke it they started building their own.

• This began their life long interest in flight.

• 1871- Alphonse Penaud flew a rubber-powered aircraft called the planophore for 131 feet in 11 seconds.

• first really stable aircraft, making it one of the most important inventions leading up to the invention of the airplane.

• Became an important research tool for aerodynamic engineers, as it allowed them to test numerous configurations of:

• wings

• rudders

• elevators

• fuselages for airworthiness

• Newton’s second law states that if the forces on an object are unbalanced then its motion will change. The bigger the force, the bigger the change in motion or acceleration.

F=ma

(Force= mass X acceleration)

• Newton's Third Law of Motion says that when two objects push or pull against each other,the forces that they feel are equal and opposite.

• The engine turns the propeller.

• The propeller is specially shaped to push the air backwards. This results in a reaction force on the propeller that moves the aircraft forwards. (Thrust).

• Energy: The ability of an object do work. Has units of Joule (J) or newton-meter (Nm).

• Kinetic Energy: Energy of motion.

KE=1/2mv2

• Potential Energy: Stored energy.

Ug=mgh

• Work: The amount of energy transferred by a force acting through a distance. Unit of Joule (J).

W=F∙d

• What about for our model airplane?

• The distance around the edge of a circle (or any curvy shape) is the circumference:

C = 2πr

• We must also count the number of times the propeller travels around the circle.

Distance = (2πr) x turns

• Power: The time rate of energy transfer. Unit of Watt (W) or J/s.

P=W/t

• Steady State:to maintain an aircraft in flight, the power input has to be equal to the power output to its surroundings.

• Using some of the equations and concepts we have just learned, let’s calculate the potential energy stored in the rubber band.

• Recall that the propeller provides the thrust to move the plane horizontally.

• In the model, potential energy is stored in the twisted rubber band powering the propeller.

• When the rubber band untwists, kinetic energy is released and work is done in turning the propeller.

• Thus, the potential energy stored in the rubber band will be equal to the work.

• Recall that Work= Force X distance

• How can we measure the force the rubber band exerts on the propeller?

F=mass x acceleration (9.8m/s2)

d= 2πr (number of turns)

• For our model: W= F x (2πr) (number of turns)

• Why is the energy stored in the rubber band different when we measure it again after winding the propeller back down?

Some of the energy was lost to heat in the rubber band!

• Now that we have calculated the work, let’s calculate the power.

• How can we do this?

Power = Work/time

• This is the most important measure of energy use in transportation.

• Energy consumed per unit mass per unit distance travelled.

• Measure of energy.

• Units of J/kg/m or kWh/tonne/km.