W*s is bare, naked SI; joules is a tag of convenience (something like dm^3 and litres). Duncan
-----Original Message----- From: Fardig, Paul S. <[EMAIL PROTECTED]> To: U.S. Metric Association <[EMAIL PROTECTED]> Date: March 25, 2002 08:26 Subject: [USMA:19049] watt seconds ?? > >I have two different photographic flash units. One is rated in joules and >one in "watt-seconds," which is commonly used for flash units. Looking at >the mathematics, I see a joule is defined as a kg*m2/s2, while a watt is a >kg*m2/s3. Therefore, a watt-second would be the same as a joule, since the >seconds to the minus 3 power would become seconds to the minus 2 power when >multiplied by seconds (overall > energy times time equals power). > >Is my reasoning correct?? Any ideas why the industry would be using >"watt-seconds" instead of joules? > >Paul >
