The Physics Behind “Unstoppable”

Can they stop the train loaded with haz­ardous chem­i­cals before this “mis­sile the size of the Chrysler Build­ing” hits a pop­u­lat­ed area and “vapor­izes every­thing in front of it?” That’s the big ques­tion that dri­ves along the plot of the new Den­zel Wash­ing­ton thriller, Unstop­pable. If you don’t believe me, just watch the trail­er above. Now we get all aca­d­e­m­ic on you and ask: Is that train real­ly as pow­er­ful as a sky­scraper-sized mis­sile? And then we turn to Emory physics pro­fes­sor Sid­ney Perkowitz for the answer:

Perkowitz is a good per­son to size things up. He’s not just any physics pro­fes­sor. This physics prof wrote the book Hol­ly­wood Sci­ence: Movies, Sci­ence and the End of the World and he sits on the advi­so­ry board of the Sci­ence and Enter­tain­ment Exchange, a Nation­al Acad­e­my of Sci­ences pro­gram that tries to bring more sci­en­tif­ic accu­ra­cy to mass mar­ket enter­tain­ment. Thanks Stephen for the good tip here …

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Comments (3)
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  • DefaultProphet says:

    I thought the dan­ger in the movie was the car­go, tox­ic mate­ri­als.

  • Tanner says:

    So… some­thing about 1 mil­lion pounds did­n’t sound right to me. I did some inves­ti­gat­ing. Here’s what I found:

    “The heav­i­est train was a BHP Iron Ore train weigh­ing 79,577 tons. The 10
    loc­mo­tives and 540 ore cars ran from New­man to Port Hed­land, West­ern
    Aus­tralia, a dis­tance of 253.9 miles, on May 28, 1996.

    Do a lit­tle rough math and this comes out to 160 mil­lion pounds. Then being that I’m an engi­neer and some­how find stuff like this fun I looked up the ener­gy in TNT (4.184 Mega­Joules per kg) and using his num­bers deter­mined that the veloc­i­ty he used was less than 10 mph (4.29 meters/second). He even says him­self how impor­tant the veloc­i­ty is because that term is ‘squared’. I make no claim of being smarter than this physics pro­fes­sor but I decid­ed to re-run the num­bers…

    Using 160 mil­lion pounds and 60 mph gives an ener­gy just shy of 7 tons of TNT!

    Grant­ed it’s in a dif­fer­ent form… a train crash’s ener­gy would be released com­pa­ra­bly much more slow­ly that TNT will ignite… but still! Sor­ta cool! :)

  • Redlami says:

    What about the high­ly com­bustible car­go and the diesel fuel on board? I would think that the explo­sive release of all that poten­tial ener­gy should enter into the pic­ture as well.

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