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Snow and Rain


IVIR

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Since we learn that objects consistently gain velocity in free fall motion due to the acceleration of gravity at 10 m/s^2, why doesn't rain and snow wreck havoc since it is falling from an insanely high distance? One reason for this lack of speed, especially with snowfall, is because of air resistance and drag forces. The net force on a snowflake would be the weight (mg) minus the drag forces acting on that object. Since snowflakes are relatively porous and non-aerodynamically shaped, the drag force is relatively large. Perhaps more importantly, a snowflake barely has any mass so the force of its weight is barely noticeable. Also, by the time the snow, or rain, reaches a height where we can see it, the snowflake or raindrop has reached its terminal velocity, which is not very high. Rain does indeed travel faster than most snow due to less drag forces, but there is a specific reason that rain does not hurt us instead of simply plopping onto our skin. Rain is a liquid, so when the raindrop does hit our body, the force isn't completely transferred to our body as the water droplet splatters itself. However, large bodies of water, like a large can still exert large amounts of force without absorbing a lot of the impact force. For example, if you cliff jump from an extremely high distance into water, the force of impact on the water is still extremely high. Part of this is due to relatively high surface tension of water, but the other part is that the water cannot dissipate all of the force of impact since it is a liquid, not a gas. 

These same reasons are also the reasons why hail and ice storms can cause serious damage as they are significantly more massive, and their shape/composition allows for lower drag forces. Large pieces of hail still reach a terminal velocity, but this terminal velocity along with its relatively large mass allow it to create immense damage, including puncturing car windshields. The car windshield and hail are in contact for such a little time that the impulse force felt by the windshield is incredibly large. Also for a follow up on my previous blog about bulletproof glass, a car windshield is layered with plastic as well, preventing it from shattering upon impact. This is also why bullet's penetrate car windows without shattering them for the most part.

Rain and snow cause a ton of damage across the world each year, but on the bright side, there is no need to run for cover when these infamous particles are failing from the sky. If they are large hail particles though, put your car in the garage, cover your house with steel and get inside because it is no joke.  

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