Gas has a lot of energy stored in its chemical
bonds. When gas reacts with oxygen that energy is
released and hot carbon dioxide gas is formed. The
hot gas is used to drive pistons in the car's
engine and make it move. Essentially the chemical
energy is converted to heat and mechanical energy.
Moving a 3000 pound car requires energy to
accelerate the car and then once it is up to
speed, it requires energy to keep moving because
of friction and air resistance. Neglecting
friction and air resistance, we can calculate how
much energy it takesto move a car a reasonable
distance using the following
Force = Mass *
Work = Force * Distance
gallon of gas contains about 130 megajoules (or
130,000,000 joules) of energy.
Mass = 3000 pounds ~ 1400
A reasonable acceleration
might be from 0 to 60 miles per hour in 20seconds
which corresponds to a constant acceleration of
So at this
acceleration for 20 seconds, the car will travel
260 meters or 0.16 miles.
1400 kg *
1.3 m/s2 = 1820
1820 Newtons * 260 meters =
470,000 Joules is less than
5% of the energy stored in 1 gallon of gas.
However we must also consider that car engines are
generally only20% efficient and that friction and
air resistance also increase the energy
requirement for moving a car. Even when these
factors are accounted for, gas still stores ample
energy to move a 3000 pound car.
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