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Osiris
2005-Sep-22, 06:03 PM
I wanted to know if there is a mathematic way to convert fottpounds or kilometer grams into joules or something more tangible.
:question: :question:

Glom
2005-Sep-22, 06:19 PM
Erm well, for kilometre-grams, the solution is to simply multiply by 9.81m/s².

Grey
2005-Sep-22, 06:36 PM
And these days, of course, to convert say, 10 foot-pounds to joules, Google (http://www.google.com/search?hl=en&q=10+foot+pounds+in+joules) will do the job for you nicely.

jfribrg
2005-Sep-22, 06:55 PM
And these days, of course, to convert say, 10 foot-pounds to joules, Google (http://www.google.com/search?hl=en&q=10+foot+pounds+in+joules) will do the job for you nicely.

As has been noted before its also great if you need to know the speed of light in furlongs per fortnight (http://www.google.com/search?hl=en&lr=&q=speed+of+light++in+furlongs+per+fortnight)

Osiris
2005-Sep-22, 08:18 PM
yeah, I wanted to convert the power exreted from one gram of antimatter touching one gram of matter and what energy that would convert to. It's approximately 90 billion kilometer grams, but I didn't know exactly what that was other than the exact amount of energy needed to push one gram of matter 90 billion kilometers.

Still I'm not quite sure how to measure such an explosion realsically, like the radius of the explosion, or damage done and energy exerted.

While people are still around what exactly is a joule. (I'm no scientist, or even, I'll admit, done with junior high.

swansont
2005-Sep-22, 08:38 PM
yeah, I wanted to convert the power exreted from one gram of antimatter touching one gram of matter and what energy that would convert to. It's approximately 90 billion kilometer grams, but I didn't know exactly what that was other than the exact amount of energy needed to push one gram of matter 90 billion kilometers.

Still I'm not quite sure how to measure such an explosion realsically, like the radius of the explosion, or damage done and energy exerted.

While people are still around what exactly is a joule. (I'm no scientist, or even, I'll admit, done with junior high.

90 billion kilometer grams is not the energy it would take to push a gram 90 billion kilometers. If the object is already moving at a constant speed, you don't do any work on it. That motion, or it's equivalent, pushing 90 billion grams 1 kilometer, or 90 trillion grams a meter, could be accomlished with very little energy. It just wouldn't happen very fast.

The relevant term here is work, which is the dot product of force and displacement.

A Joule is the amount of energy needed to move a kilogram a distance of one meter, under an acceleration of one meter per second squared. (That acceleration can be because the object is changing speeds or because you are in a gravitational field that has that acceleration) Here the force would be 1 Newton, so you could also say a Joule is the work done in exerting a 1N force (on anything) through a displacement of 1m.

Eta C
2005-Sep-22, 08:38 PM
E= mc^2 my friend. For two grams total and a speed of light of 3*10^10cm/sec you get an energy release of 18x10^20 erg where one erg has units of gram cm^2/sec^2. This corresponds to 18x10^13 Joules where one joule has units of kg m^2/sec^2 (1000 grams to the kg. 100 cm to the m gives the coversion factor of 10^7 ergs to the joule.

The joule is the metric unit of energy. Like all energy units it has dimensions of mass times distance squared divided by time squared.

Eta C
2005-Sep-22, 08:42 PM
Also, you need to be clear in your units. Energy and power mean different things to a scientist. Energy, as we've pointed out has units of joules. Power, on the other hand, is a measure of energy transfer per unit time. In metric units the watt , corresponding to a joule/sec, is the unit of power. I've given you the energy released by 2 grams of matter-antimatter conversion. Without knowing how long that takes (days, seconds, nanoseconds?) there can be no definition of power.

Grey
2005-Sep-22, 10:32 PM
And if you're curious what roughly 10^14 Joules (or any other amount of energy) corresponds to, this (http://en.wikipedia.org/wiki/Orders_of_magnitude_%28energy%29) is a pretty good place to look. It's the equivalent of about 20 kilotons of TNT, or a tenth of the electricity production in Togo. :)

hhEb09'1
2005-Sep-24, 04:52 AM

01101001
2005-Sep-24, 05:09 AM
E= mc^2 my friend. For two grams total and a speed of light of 3*10^10cm/sec you get an energy release of 18x10^20 erg where one erg has units of gram cm^2/sec^2.
I've mentioned it before in BABB, but it so delights me that Google Calculator has an understanding of what you just wrote:

Input: 2 grams in ergs
Output: 2 grams = 1.79751036 × 1021 ergs

Input: 2 grams in joules
Output: 2 grams = 1.79751036 × 1014 joules

Input: 2 grams in foot pounds
Output: 2 grams = 1.3257756 × 1014 foot pounds