Energy is present in various forms all around us and is thus one of the most important topics in science and engineering. In secondary schools, students learn the basics of energy and energy transfer by studying potential and kinetic energy of several systems. These concepts can be taught through the use of rubber bands, as the energy stored in a rubber-band is a form of elastic potential energy. Therefore, a rubber band powered airplane can be a very interesting toy for demonstrating the fundamentals of energy and energy transfer. The following are some topics that can be taught about rubber-band powered airplanes.
When the Wright Brothers were small children their father gave them a rubber powered aircraft which resembled a helicopter. They played with it until it broke and then they built several of their own. They later claimed that their experience with the toy fuelled their interest in flying, resulting in the invention of manmade flight.
In 1871, French scientist Alphonse Penaud, the same man that built the toy the Wright Brothers played with, amazed people by flying a rubber-powered aircraft called the planophore for 131 feet in 11 seconds. It was the first public demonstration of a legitimately stable heavier-than-aircraft, making it one of the most important inventions leading up to the invention of the airplane.
For the following 50 years, rubber-powered airplanes were an important research tool for aerodynamic engineers, as it allowed them to test numerous configurations of wings, rudders, elevators, and fuselages for airworthiness without building full-size aircrafts.
Rubber-band powered aircraft, or then called torsion-powered aircraft, became a popular toy in the late 1800’s and has remained popular ever since, with people still building them today all over the world and entering them in competitions.
How a Rubber-Band Powered Airplane Works
An airplane moves forward when the plane’s engines push fast moving air out behind the plane by propeller or jet. The propeller provides the thrust to move the plane horizontally. In the rubber-band powered airplane, potential energy is stored in the twisted rubber band which powers the propeller. The propeller provides the thrust, which pushes the airplane forward according to Newton’s Third Law. The plane is able to move through the air and fly by lift generated by the shape of the wings. During take-off and landing the speeds of the aircraft are slower which in turn gives a smaller value for the lift, thus the lift force acting on the airplane is at its weakest here. Extra lift can be achieved at slower speeds by changing the shape of the wing using ailerons and flaps which increase the surface area of the wing.
Energy and Energy Transfer
Some concepts that could be taught or reviewed are potential energy (U) and kinetic energy (K), as the potential energy that is stored in the twisted rubber band is converted to kinetic energy which powers the propeller. Next, work should be reviewed as it is the amount of energy transferred by a force acting through a distance.
As well, the concept of power should be taught, as it is the time rate of energy transfer. From there, the idea of steady-state should be discussed and the notion of transport cost could be introduced. Finally, we could compare the transport cost of the model airplane with a real size jetliner.
Some useful equations:
Rough Lesson Plan (55-75min)
1. Introduce the topic and give a power point presentation to the class (20-25min)
• Review the four forces acting on an airplane- lift, gravity, thrust and drag.
• Review potential, kinetic energy and work.
• Review Newton’s Second and Third Laws of motion.
• Introduce power, steady-state and transport cost.
2. Calculations (10 min)
3. Students will build their models (30min)
4. Testing the airplanes (10min)
Model airplane kit
White glue or fast drying wood glue and glue stick
Alphonse Pénaud. (2009). In
Encyclopædia Britannica. Retrieved October 20, 2009, from Encyclopædia
Britannica Online: http://www.britannica.com/EBchecked/topic/1312623/Alphonse-PenaudSerway,
Serway, R. A., & Jewett, J. W. (2004). Energy and Energy Transfer. In R. A. Serway, & J. W. Jewett, Physics for Scientists and Engineers with Modern Physics 6th edition (pp. 181-205). Belmont: Thomson Learning.
Serway, R. A., & Jewett, J. W. (2004). Potential Energy. In R. A. Serway, & J. W. Jewett, Physics for Scientists and Engineers with Modern Physics (pp. 217-236). Belmont: Thomson Learning.
White, D. (2009). Model airplane powered by elastic rubber band. Retrieved September 27, 2009, from Model airplane powered by elastic rubber band: http://www.rubber-power.com/