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Question
If both friction and air resistance were eliminated from acting on the swinging pendulum, would gravity act on the pendulum to slow it down and eventually stop?
Asked by: John Barrus
Answer
No, it wouldn't. If all friction and air resistance
was eliminated (plus, the losses due to deformation
of the string and the like) the pendulum, under ONLY
the effect of gravity, would keep swinging indefinitely.
That's because gravitation is a 'conservative' force,
it does not drain any energy from the object moving under
it effect, it just converts the energy from one form
to another. When the pendulum reaches either end at
its highest point, all the energy is potential energy,
and the kinetic energy is zero. At the bottom of the
swing, the kinetic energy is maximum, while potential
energy is minimized. No energy is transferred out of
the system, so it must keep moving. In the presence
of friction however, energy is removed from the system
in the form of heat. (The air heats up a little, the
contact point of the string heats up a little... etc).
Answered by: Yasar Safkan, Ph.D. M.I.T., Software Engineer, Istanbul, Turkey
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