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| Forces on a falling insect. © Eugene Brennan |
One
of the reasons insects don't hurt themselves when they fall is because
they have a low terminal velocity and are travelling relatively slowly
when they reach the ground. Terminal velocity is the maximum velocity
attained by a falling body in a fluid such as air or water and subject
to a force called drag,
(resistance to motion). For humans, it's around 120 mph or 54 m/s lying
flat. For an insect, it's typically around 2 m/s. Once the increasing
drag force balances the weight (another force), there's no net force and
an object stops accelerating (Newton's second law of motion). Also when
an insect hits the ground, because it has such a small mass, the
g-force on its body is small because it has to shed so little momentum,
and that also helps prevents damage. So it's a combination of low
terminal velocity, small mass and also having an outer protective layer
or exoskeleton that gives them protection.
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