- #1

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E = 2734.2 joules per gram

P = 2.73 x 109 watt/gram

q: How can this conversion work?????

E = 21000 joules per gram

P = ?

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- Thread starter jamiebean
- Start date

- #1

- 55

- 3

E = 2734.2 joules per gram

P = 2.73 x 109 watt/gram

q: How can this conversion work?????

E = 21000 joules per gram

P = ?

- #2

- 434

- 247

what do you want to convert? Joule is unit of energy, Watt is unit of Power. Those are different physical quantities.

E = 2734.2 joules per gram

P = 2.73 x 109 watt/gram

q: How can this conversion work?????

E = 21000 joules per gram

P = ?

- #3

- 87

- 40

1 watt = 1 joule per second

- #4

- 55

- 3

what do you want to convert? Joule is unit of energy, Watt is unit of Power. Those are different physical quantities.

E=energy

P=power

s the conversion above possible??

- #5

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- #6

A.T.

Science Advisor

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If you know the time.s the conversion above possible??

- #7

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If you know the time.

I don't think that conversion is the correct word here. We could also ask (as analogy to Energy and Power): What is the conversion between Distance and Speed? It doesn't have any physical meaning. But we can say there is close relationship between them, when describing motion of an object.

- #8

CWatters

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E = 2734.2 joules per gram

P = 2.73 x 109 watt/gram

q: How can this conversion work?????

E = 21000 joules per gram

P = ?

If the two systems are similar I would try using ratios (scaling)

P2/E2 = P1/E1

So..

P2 = (P1/E1) * E1

P2 = (2.73 * 10^9 / 2734.2) * 21000

Without more information it's not possible to say if this is the correct approach. Not everything scales linearly like this.

- #9

Mister T

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example)

E = 2734.2 joules per gram

P = 2.73 x 109 watt/gram

q: How can this conversion work?????

##\frac{2734.2 \ \mathrm{J/g}}{2.73 \times 10^9 \ \mathrm{W/g}}\approx 1.00\times10^{-6} \ \mathrm{s}##

This calculation tells us that if you delivered energy at a rate of 2.73 x 10

It's like saying your position changes by 60 miles every hour when you move at a speed of 60 mi/h. If you do this for, say 2 hours, you'll travel a distance of 120 miles. Note that I'm not converting 60 mi/h to 120 mi. Again, there are no conversions here.

Conversions are present when two quantities are measuring the same thing but in different units. When you measure a speed of 60 mi/h you're measuring a speed, not a distance. And when you measure a distance of 120 mi you're measuring a distance, not a speed. Speed is the rate at which distance changes.

The watt is a unit of power, not energy. The joule is a unit of energy, not power. Power is the rate at which energy is transferred.

- #10

OmCheeto

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Can't see that anyone has done it so far, but I'd like to point out that the equations are incorrect.

E = 2734.2 joules per gram

P = 2.73 x 109 watt/gram

q: How can this conversion work?????

E = 21000 joules per gram

P = ?

Joules/gram is "specific energy", not just energy.

Likewise, watts/gram is "specific power". Which happens to be such an obscure thing, that wiki doesn't even have an entry for it.

They do list two examples though, in their "

Stars/hydrogen: 1.84 watts/gram

Plutonium: 1940 watts/gram

Plutonium: 1940 watts/gram

This might seem trivial, and it appears that everyone has simply worked around it, as "grams" simply cancels out, but it confused me at first.

In my confusion, I decided to find out the specific energy of something, and randomly picked apples.

Serendipitously, they have a surprisingly similar specific energy to your number: 2200 joules/gram

From that, I determined that I'd have to eat 6,700 apples per second, at the given "specific power".

Which is when I think I went back to your original post, as that seemed like a lot of apples to consume, per second.

- #11

russ_watters

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Yes, but that's just the chemical energy released in digesting apples. You'll need a lot less if you fuse them.Serendipitously, they have a surprisingly similar specific energy to your number: 2200 joules/gram

From that, I determined that I'd have to eat 6,700 apples per second, at the given "specific power".

Which is when I think I went back to your original post, as that seemed like a lot of apples to consume, per second.

- #12

Mister T

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Yes, but that's just the chemical energy released in digesting apples. You'll need a lot less if you fuse them.

All you'd need is a tiny piece of one of those apples, provided you had a comparable amount of anti-apple.

- #13

CWatters

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- #14

CWatters

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I think we need the OP to provide more context to his question.

- #15

OmCheeto

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Yes. I remember the "power to weight" ratios listed for cars, back when I was a youngster.

Interesting how "specific power" is mostly only a concern of rocket scientists, 16 year olds, and electric car manufacturers.

hmmmm........

Yes.

Where is that OP?

- #16

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a watt-second is a joule.

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