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Energy of a vehicle in a crash

  1. Sep 24, 2015 #1
    Hello all, I am in need of some help. I work for a fire department who had a significant fire truck crash last summer. Because of this, my department has set about making a training program for our drivers. Lucky me, I am in charge of said program.

    So I need some help.

    Here is the story. Last summer one of our Ladder Trucks ( fire truck with the big long ladder on the top of the truck that extends out, not a fire engine that has water) was traveling around 58 mph on a curved road then is lost traction, slide and rolled. No one was seriously hurt.

    Here is what we know. Said ladder truck was traveling around 58 MPH and weight 62,500 lbs. I know, using the formula for kinetic energy, ( KE= 1/2 Mass X Velocity squared) that this truck produced 7,016,409.78 ft lbs or 3,508 tons of energy.

    What I am looking for is a way so show the members of my department what that much energy looks like. As in, that kind of power in an explosion, or a wrecking ball destroying a building. I need a way to relay to my guys, the power that they are driving down the roads and highways every day.

    Luckily when this truck crash, it only hit a telephone pole a picket fence and a few cars. The extent of the damage was very little in comparison to what could have happened.

    I have searched the web for a way to show this and have come up with nothing. Someone suggested I try a Science blog, so I leave it up to you. What have you got ????

    And thanks for the help.
  2. jcsd
  3. Sep 24, 2015 #2


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    Science Advisor
    Gold Member
    2017 Award

    HI there
    welcome to PF :smile:

    OK for a start, KE isn't measured in tons, its measured in Joules
    it would probably be a good idea to convert the imperial mph and lbs to metres/sec and kg's
    have a look at the wiki link ...

    There are other wiki entries that compare various blasts with the KE released in Joules

    have a little search

  4. Sep 24, 2015 #3

    Thanks for the link. I had looked a a chart and converted everything from jules to pounds (tons) and mph. When dealing with firemen, the simpler the better. We do understand joules, but only in the settings of the defibrillator when used for a CPR. I am trying to keep the explanations as easy for the common person to understand as possible.
  5. Sep 25, 2015 #4


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    You cannot convert from joules to pounds. The one is a unit of energy. The other is a unit of mass.

    However, you can convert from foot-pounds to foot-tons. Those are both units of energy. That is the conversion you have actually done. 7 million foot pounds is equal to 3500 foot tons. That is the energy required to lift 3500 tons one foot. Or the energy required to lift one ton 3500 feet into the air.

    Or the energy required to lift one 30 ton truck by a little over 100 feet. Which makes sense since rolling down a hill that high would give the truck a speed of 58 mph.
  6. Sep 25, 2015 #5


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    Staff: Mentor

    Well, at that mass and velocity, the truck has about 9,529,377 joules of energy, or 9.5 mega-joules. This is equivalent to the energy given off by about five pounds of TNT exploding. So it is, literally, like driving a bomb.

    Or, if you prefer, tell them the truck has the same kinetic energy as a motorcycle moving at 500 mph.
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