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Using a Jeep to Estimate the Energy in Gasoline
(10 mph)/(11 sec) = 0.91 mph/sec = 0.40 m/sec2
and the force slowing the Jeep:
(1400 kg) x (0.40 m/sec2) 560 nt
This force is the same force that must be overcome when driving the Jeep at constant speed. Since 20 miles/gal = 32,000 m/gal, the energy in j, expended by burning a gallon of gasoline to overcome 560 nt of force over the distance of one mile, is
(560 nt) x (32,000 m/gal) 2 x 107 j/gal.
Since engine efficiency is 20%, the actual energy expended must be about 5 times the above stated amount, or
the difference showing up as waste heat. Thus, burning a gallon of gasoline releases about 108 j of energy.
Exploding a ton of TNT liberates about 4 x 109 j, so that a gallon of gasoline is equivalent to about 50 pounds of TNT.
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