Verification of Conservation of Energy

  1. How is conservation of energy experimentally verified if some energy is dissipated, for example, as heat in air friction or friction with a road?
  2. jcsd
  3. Vanadium 50

    Vanadium 50 17,740
    Staff Emeritus
    Science Advisor
    Education Advisor

    By doing other, more controlled experiments. Making a bad measurement is not part of the scientific method.
  4. Ok. I guess I don't understand the extent to which experiments can be controlled. How would one measure energy lost via friction with a road?
  5. russ_watters

    Staff: Mentor

    In a lab environment, with a dnyo or sort of road treadmill.
  6. Nugatory

    Staff: Mentor

    The energy "lost" to friction shows up as heat somewhere in the system. Thus, we need to design the experimental apparatus in such a way that any heat leaving the exoerimental apparatus is detected and counted; usually we do this by very carefully monitoring the temperature.

    For example, a propeller turning in a container of water doesn't appear to conserve energy. We keep on adding energy to it by turning the shaft, yet its kinetic energy remains stubbornly fixed as it keeps turning at the same speed. But if we also measure the temperature of the water in the container (and insulate the container well enough that it doesn't leak heat out into the environment) we'll find the "missing" energy in the increasing heat of the water.
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