How Does the Energy Density of a Lead-Acid Battery Compare to Gasoline?

AI Thread Summary
The energy density of a fully charged 15.0 kg lead-acid battery delivering 1450 W for 1 hour needs to be calculated correctly. The initial calculation shows a misunderstanding of units, as Watts represent energy per time. To find the energy density in MJ/kg, the total energy delivered by the battery must be calculated first, which involves multiplying power by time. After finding the total energy, it should be divided by the mass of the battery to obtain the correct energy density. Accurate calculations reveal that the energy density of lead-acid batteries is significantly lower than that of gasoline.
aaronb
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Homework Statement


A fully charged 15.0 kg lead-acid battery can deliver power 1450 W for 1.0 hr. (For comparison, the "heat of combustion" of gasoline is about 44 MJ/kg.)

Battery _____ MJ/kg

Homework Equations


Unit conversion problem
1W = 1 J/s

The Attempt at a Solution


(1450 J/s / 15kg) = 96.7/10^6 = 9.6 *10^-5
 
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You should notice immediately if you kept your units that your final answer does not have the units of MJ/kg as I see your answer requires. Remember, Watts (or Power) is a unit of energy per time. You're missing one part of the calculation.
 
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