Sunday, October 6, 2013

Hollywood Physics

I was watching Pacific Rim this weekend and thought of an amusing calculation to do.  At one point in the film, a Kaiju (giant sea monster) and a Jaeger (giant robot designed to fight Kaiju's) were fighting at the edge of the atmosphere.  The Kaiju is slain and the Jaeger, named Gypsy Danger, was falling back to earth.  Ignoring all other forces, I was curious as to the gravitational potential energy of the Jaeger.  I looked up how much Gypsy danger weighed, and from a fan site, found that it weighs 1,980 tons.  Converted into kilograms, that's 1.8x10^6 kg.  Assuming it was near the edge of Earth's atmosphere when it began falling, that would mean it was 80km (80000m) above the surface of the Earth (edge of the mesosphere).  The formula for gravitational potential energy is PEg=mgh.  That means the gravitational potential energy is (1.8x10^6)*(10)*(80,000) = 1.44x10^12 J.  That is an enormous amount of energy.  Put into perspective, it's recommended that average person takes in 2,000calories a day.  Converted into joules, that's 8368J.  You would need 172,084,130 people to consume that much energy.

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