Falling Objects and Air Resistance:
Gravity is the physical force that pulls apples as well as humans toward the
center of the earth. On the earth objects experience a fixed acceleration due
to the force of gravity. The force is applied constantly and works kind of like
continually compounding interest. The earth actually applies a one G force on
everything near its surface. A force of this magnitude creates an acceleration
of 9.8 meters per second. This means that every object that is in the process
of falling travels 9.8 meters per second faster than the second before. So by
the end of the first second it will be falling at 9.8 meters per second and the
second second …that’s right 19.6 meters per second.
Heavy objects and light objects fall at the exact same speed. A heavier object
has a stronger gravitational field and exerts more force back on the earth but it
still falls at the same rate as a lighter object because it has more of what is
called inertia. Inertia is an object's resistance to movement and it increases
with mass. A heavier object is harder to move because of its inertia but the
force between it and the earth is stronger. Because these forces effectively
even out, all objects fall at the same speed.
You then ask: “why does a feather fall more slowly than a brick?” The feather
has more surface area when compared to its mass. The proportionately
higher surface area of the feather creates more drag, in the form of friction,
with the air molecules as the feather falls. If you drop a feather and a brick
from the same height on the earth the brick will hit the ground first. If you drop
both on the moon, where there is no atmosphere, they will hit the lunar surface
at the same time.
Because feathers naturally have very high surface areas they enable birds to
cheat gravity. Feathers make flying easier on birds by increasing air
resistance and slightly decreasing the affects of gravity on the bird.
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