There are four types of resistance. Static resistance gives the operator a bit
of a counterforce in the early milliseconds of operation, but operates freely
afterward. Elastic resistance feels like a spring- loaded knob; once the con-
trol has turned to a desired setting, it reverts to its initial position as soon as
the operator releases it.
Viscous resistance is proportional to the speed of motion. The dashpot
on a utility door allows the door to close at a preset speed once the user has
set it in motion. The objective is to prevent the noise or damage that could
arise from slamming the door or the operator’ ...
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