Semi tanker drives through flooded road - GIF

[markonevet]

Semi tanker drives through flooded road.

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Previously:

Car catches fire after driving through flood - GIF
Arizona flash flood - GIF
Flash flood swallows construction site - GIF
Flash flood smashes restaurant facade - GIF
Flash flood barriers - GIF

Fact: Water is 832 times denser than air, so a 10 mph flowing river/stream that has a submerged object is pushing with a force equal to a wind blowing at 8,320 mph. When you see an equation like that it should not be surprising when big objects get moved so easily with swift-flowing water. It is deceiving and no wonder so many ignorant people get caught and drown.

[cmarlow]

Yup, and you mention submerged objects, so lets consider buoyancy. If the object is in the water it is trying to float, even if it is denser than the water. even if it is only partly submerged.. Its weight is reduced by the volume of the water it displaces, which means it has even less downforce to produce friction and resist being pushed. If the object can float there is no resistance at all unless it is tied to an anchor.
If you try wading through moving water and it is only ankle deep the water is trying to float your feet and you will have about 7 or 8 % less downforce because of it. If you are in the water waist deep you have lost almost half of your downforce as well as greatly increasing the area the water is pushing against. Waders have been drowned in fairly shallow water because when they got knocked over a foot got trapped between rocks or similar, holding them in the current as it washed over them and making it impossible for them to get up.

[mklotz]

Fact: Water is 832 times denser than air, so a 10 mph flowing river/stream that has a submerged object is pushing with a force equal to a wind blowing at 8,320 mph. When you see an equation like that it should not be surprising when big objects get moved so easily with swift-flowing water. It is deceiving and no wonder so many ignorant people get caught and drown.

Your "equation" is simplistic but I think there is a problem. If you're going to equate the kinetic energies of air and water, I think the equation should look like

ma * va² = mw * vw²

where:

ma = mass of air
va = speed of air
mw = mass of water
vw = speed of water = 10 mph


For equivalent volumes of air and water we can substitute the appropriate densities for the masses, which leads to:

mw = 832 * ma

and the equation becomes:

va = vw * sqrt (832) = 10 * 28.8 = 288 mph

The original equation is too simplistic and ignores some important effects but, taking it as presented, the 8320 mph wind seems unrealistic.

The 832 is a bit off too.

Water density is 1000 kg/m³
Air density is 1.225 kg/m³

1000 / 1.225 = 816.33