- #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 = ?

- B
- 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

- 75

- 33

1 watt = 1 joule per second

- #4

- 55

- 3

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

P=power

s the conversion above possible??

- #5

- 434

- 247

- #6

A.T.

Science Advisor

- 11,066

- 2,530

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

- #7

- 434

- 247

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.If you know the time.

- #8

CWatters

Science Advisor

Homework Helper

Gold Member

- 10,532

- 2,298

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

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 = ?

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

Science Advisor

Gold Member

- 2,608

- 856

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

E = 2734.2 joules per gram

P = 2.73 x 109 watt/gram

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

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

Gold Member

- 2,143

- 2,598

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

Mentor

- 20,288

- 6,870

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

Science Advisor

Gold Member

- 2,608

- 856

All you'd need is a tiny piece of one of those apples, provided you had a comparable amount of anti-apple.Yes, but that's just the chemical energy released in digesting apples. You'll need a lot less if you fuse them.

- #13

CWatters

Science Advisor

Homework Helper

Gold Member

- 10,532

- 2,298

- #14

CWatters

Science Advisor

Homework Helper

Gold Member

- 10,532

- 2,298

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

- #15

OmCheeto

Gold Member

- 2,143

- 2,598

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

- 375

- 21

a watt-second is a joule.

- Last Post

- Replies
- 7

- Views
- 1K

- Last Post

- Replies
- 23

- Views
- 3K

- Replies
- 15

- Views
- 12K

- Replies
- 1

- Views
- 3K

- Replies
- 1

- Views
- 699

- Last Post

- Replies
- 38

- Views
- 5K

- Last Post

- Replies
- 10

- Views
- 3K

- Last Post

- Replies
- 14

- Views
- 7K

- Last Post

- Replies
- 3

- Views
- 2K

- Last Post

- Replies
- 5

- Views
- 754