Answer 1:
That is a great question. Gravity is, of course,
different, and can be stronger or weaker,
depending on the planet. The drag on the ball
will also change, depending on the pressure of the
atmosphere, the temperature on the surface, and
the type of gas in the atmosphere. There is a
nice website from NASA
click here
that talks about aerodynamics on other planets.
The density and viscosity of the gas in the
atmosphere are the main material properties
required to figure out the drag force on the
ball. This depends on the type of gas, the
pressure of the gas, and the temperature. Once
you have the viscosity (and density) of the gas,
and if you figure out how fast you can kick a
ball, and how big a ball you’re kicking, you can
figure out the “Reynolds number” for that
ball. This is a quantity that is very important
in fluid dynamics and gas dynamics, and
determines how the fluid behaves. From the
Reynolds number, you can figure out a “drag
coefficient” for the ball,
dragsphere
which tells you how big the drag force is on
the ball.
Generally, the drag force will be
F = CD * rho * V2
where rho is the density of the gas, CD is the
drag coefficient (from the figure on the
website above), and V is the velocity (or
speed) of the ball.
Most of the time, CD will be between 1.5 and .5
— so doesn’t depend very strongly on the Reynolds
number (or viscosity), although there are
conditions where viscosity will really matter
(where CD is much bigger or much smaller). So
most of the time, the main difference in drag
force on a ball kicked at 30 mph on Earth vs. on
Mars will come from the difference in atmospheric
densities (rho) on the two planets.
Play around on the NASA website — there are
lots of interesting details about other planets,
that make you realize how different even everyday
life can be...
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Answer 2:
The density of the atmosphere determines
drag. Most sources that would tell you what
the surface gravity of a planet is would also tell
you some things about the planet's atmosphere.
Incidentally, I don't know how much drag
affects soccer ball kicks. However, here's
something for you to check out: South American
peoples play soccer on the Altiplano, a plateau in
the Andes mountains at about 3,000 meters
elevation. The air pressure at that altitude is
about 80% or so of the pressure at the surface,
ballpark. Does this affect drag noticeably?
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