Friday, November 30, 2012

The Physics of Hurricane Sandy


By Elizabeth Morea

Hurricane Sandy was a very strong and powerful super storm that hit my coastal hometown in New Jersey. The destruction caused by the hurricane was unbelievable. Entire buildings and trees were ripped out of the ground due to the high wind speeds. In order to cause this much destruction I decided to find out an estimate of what the energy of the hurricane was. To do this I first had to find the  inertia of the hurricane. I estimated the hurricane to be a cylinder of air with the each area of the cylinder having the same angular velocity. According to the website “Our Amazing Planet”, the super storm had hurricane-force winds of about 120km/hr, as a level 3 hurricane, extending up to 175 miles from the center of the storm.  Based on data from NASA, the hurricane had a height of about 13km.  Because of the assumption that the hurricane is a cylinder the equation for the moment of inertia is ½ MR2. The mass of the hurricane can be found by multiplying the volume of the cylinder times the density of the air in the hurricane.

Density of Air= 1.3kg/m3
VcylinderpR2h=p((175mi)(1609m/mi))2(13x103)=3.24x1015m3
M=(1.3kg/m3)(3.2x1015m3)=4.16x1015kg

Using this mass the Inertia can be found and thus the kinetic energy of Hurricane Sandy can be found.

KE= (1/2)Iw2= (1/2)(1/2)(M)(R2)(voutside/R)2= (1/4) (M)(v2outside)

      KE=(1/4) (4.16x1015kg)((120km/h)((1km/h)/(3.6m/s)))2=1.16x1018J

Hurricane Sandy had an energy of  about 1.16x1018J. This was the rotational kinetic energy of the storm and in reality was probably even greater with the added energy contributed by the storm surge of water it created when it hit my coastal hometown in New Jersey. 

1 comment:

  1. density of air decreases with height. It is hardly 1.3 at a height of 13 km...

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