What one gold star is worth

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• Most people don t have a good intuitive feeling for how much energy 50 watt hours is. So I played around with numbers for a while, assuming a 2800-pound
Message 1 of 2 , May 26 11:01 PM
Most people don't have a good intuitive feeling for how much energy
50 watt hours is. So I played around with numbers for a while,
assuming a 2800-pound Prius.

Going from 0 to 60 on the level is as much energy as two and a half
gold stars.

One star is enough energy to lift the car 47 feet straight up, or to
go from 0 to about 35 mph.

One gold star is equal to the energy expended running four horsepower
for one minute, or sixteen horsepower (high speed cruise) for fifteen
seconds. It's the amount of mechanical work a championship athlete
could do in a quarter of an hour.

Using Shinichi Abe's figures for peak fuel efficiency (225 grams per
kilowatt-hour, reported in Automotive Engineering International), a
Prius would have to burn at least 11 grams of gas to equal one gold
star. That's a little more than a third of an ounce.

Four gold stars cover the operating range of the battery pack.

36 gold stars cover the maximum charge range of the battery pack,
which is a meaningless quantity to anyone whose battery pack is
controlled by the Prius computer.

An emergency stop, by the way, dissipates something like 170
kilowatts average from start to finish. That's more than enough to
trip the main breaker in your house if it were in electrical form.

Playing with these numbers really makes me appreciate what brakes go
through, and how much energy is stored in gasoline.
• A few more quick calculations, if my math is correct: One star = 50 wH = 180,000 joules = 43 food calories = 2e-9 grams (in e=mc^2 equivalence) .micah
Message 2 of 2 , Aug 15, 2001
A few more quick calculations, if my math is correct:

One star = 50 wH
= 180,000 joules
= 43 food calories
= 2e-9 grams (in e=mc^2 equivalence)

.micah

--- In toyota-prius@y..., revocable@p... wrote:
> Most people don't have a good intuitive feeling for how much energy
> 50 watt hours is. So I played around with numbers for a while,
> assuming a 2800-pound Prius.
>
> Going from 0 to 60 on the level is as much energy as two and a half
> gold stars.
>
> One star is enough energy to lift the car 47 feet straight up, or to
> go from 0 to about 35 mph.
>
> One gold star is equal to the energy expended running four horsepower
> for one minute, or sixteen horsepower (high speed cruise) for fifteen
> seconds. It's the amount of mechanical work a championship athlete
> could do in a quarter of an hour.
>
> Using Shinichi Abe's figures for peak fuel efficiency (225 grams per
> kilowatt-hour, reported in Automotive Engineering International), a
> Prius would have to burn at least 11 grams of gas to equal one gold
> star. That's a little more than a third of an ounce.
>
> Four gold stars cover the operating range of the battery pack.
>
> 36 gold stars cover the maximum charge range of the battery pack,
> which is a meaningless quantity to anyone whose battery pack is
> controlled by the Prius computer.
>
> An emergency stop, by the way, dissipates something like 170
> kilowatts average from start to finish. That's more than enough to
> trip the main breaker in your house if it were in electrical form.
>
> Playing with these numbers really makes me appreciate what brakes go
> through, and how much energy is stored in gasoline.
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