Question

Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? what happens to its energy eventually? is it a violation of the law of conservation of energy?.

Answer 1

Answer:

Energy transforms from Potential energy to (Kinetic Energy+heat+air drag) to potential energy. The bob comes to rest as it loses its energy due to the influence of the factors from the surroundings. The bob's energy is lost eventually and no, this happening is not a violation of the law of energy conservation.

Explanation:

• For the illustration please refer to the figure attached herewith.
• The bob is given some energy in the form of potential energy at the beginning and after it is released it swings back and forth interchanging energy between the potential to kinetic and keeping the total of its energy constant.
• Only in the ideal conditions (no friction loss at the pivotal point, no air drag) the conditions described just above happen to exist. Else, where all the resistances are available: in the practical scenario, some energy gets dissipated to the environment via these factors making the total energy no longer a constant.
• As a result of this, both its potential and kinetic energy also get reduced illustrating a gradual reduction of the height the bob would rise and the speed it would swing with.
• The energy distribution, in this case, happens to be like this: Bob's total energy - lost energy = potential energy + kinetic energy.
• This lost energy is not a miracle it is nature that some energy is transformed into some other form hence this happening is not a violation of the law of energy conservation.
• In that case, energy is conserved between the bob and the environment.

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