23 Mar, 2012
PRESENTATION: In absence of friction the addition of kinetic and potential gravitational energy remains constant. The dissipative effect of friction may be quantified by straightforward geometric measurements.
- A Rolling Sphere Experiment, Adam Niculescu, Phys. Teach. 44, 157 (2006)
INTRODUCTION: The conservation of energy is a basic principle that affirms that energy is neither created nor destroyed, but only transformed between different types. In these transformations the total amount of energy remains constant, so the total amount is the same before and after each transformation. In the case of mechanical energy, if there is no friction and if no external non-conservative work is considered, the addition of kinetic and potential energy is constant. This is known as The Principle of Conservation of Mechanical Principle.
OBJECTIVE: To demonstrate the Conservation of mechanical energy.
MATERIALS: Metallic balls, a rubber rail, wooden bars, and a wooden stand.
SETUP: The rubber rail will be given a double wedge shape with two mobile wooden bars that will allow changing the angle with the horizontal. The ball is let go at one end of the rail and will go down and then up the other wedge, oscillating until it stops.
EXPLANATION: As the mechanical energy is conserved, the ball should go up and down indefinitely, but the action of an external agent such as friction eventually stops the ball movement. The friction of the ball with the air and with the rubber rail is not a conservative force.
CONCEPTS: Conservation, mechanical energy, kinetic and potential energy.
- Tipler P.A. Física. Barcelona: Reverté, 2010.
- De Juana J.M., Física General, Pearson, 2009.
- Serway R.A y J.W.Jewett. Física, Thomson-Paraninfo, 2010.
STUDENTS 2012-2013: Felipe Rodríguez, Efrén Rodríguez, Lois Liste, Lara Suárez
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