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Good ole Sandy...

DavidStack

Entry posted by DavidStack

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In the wake of the costly hurricane Sandy, its interesting to look at how physics explains the dangers of those extremely powerful winds. In my backyard, the gusts snapped a horizontal branch off of one of my trees on monday night, so I wondered how dangerous it would be if I was standing under the branch when it hit the ground. The branch was about 4 meters high. Assuming that the wind was moving completely horizontal and perpendicular to the branch, the branch would have had no vertical force acting on it, neglecting air drag. Thus, you can calculate the vertical speed of the branch upon hitting the ground with conservation of energy. K = U, so .5m*v^2 = mgh, so v = (2gh)^(1/2), so v = (2*9.8*4)^(1/2), so v = 8.85 m/s. The wind was moving at 35 mph (15.6 m/s), so that is the horizontal speed of the branch. Given these two speeds, the final speed of the branch is calculated by taking the square root of the sum of the squares, so v = 17.94 m/s (40.13 mph). I don't know about you, but I certainly would not want anything crashing into me at 40 miles an hour, so Sandy was dangerous even as she was cooling off.

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denverbroncos

Very cool, but also very scary. The coast was hit so much harder than the rest of us, if Sandy was throwing branches at 40 miles per hour while cooling off how dangerous would it have been to be out in the peak of the storm.

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lshads

Branches are especially damaging, but you could still survive! When they make contact with surfaces such as a house, they have a high impulse since it can remain in contact with the siding. Likewise, those who flinch will also take on more pain, half because their muscles tense up, and half because they are taking more total force. Those who are able to just take on the initial shock will most likely incur less damage to their body.

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