The mass of the train should be the same (recap: car of a train is heavier than a truck [we've heard the term oneton-truck so let's say a truck weighs 1 ton]. It's probably more than 10 trucks but less than 100 so we say 30 tons. And there are 6 cars so about 2 * 10^5kg.
In the Spider-man question we said the train was going about 30km/hr. But this is Metropolis, the city of tomorrow! So let's say the city has levitating Shinkansen which can travel upto 600km/hr. Since it probably didn't have time to reach it's fastest speed in the city we'll say the train has a velocity of 100km/hr = 100km/hr * 1000m/km * 1hr/3600s = 100/3.6 m/s = 30m/s when it comes flying of the tracks.
Just like before we can find it's original kinetic energy (KE = 0.5 * m * v^2 = 0.5 * 2 * 10^5kg * (30m/s)^2 =10^8J). That's an order of magnitude larger than the train Spidey stopped.
But here's the second kicker: whereas Spider-man took 10 blocks to stop the train Supes has only half a block if this train isn't going to crash into a crowded skyscraper. So remember there's 10 blocks in every kilometer - so half a block is about 50m.
So the force is F=W/d = 10^8J / 50m = 5 * 10^6N.
That implies Superman is about 500 times stronger than Spider-man. If that's not a 'super' Fermi problem, I don't know what is.
All this talk about Superman is a good excuse for me to put up this link to a Comedy.com post
6 days ago