Wikipedia:Reference desk/Archives/Mathematics/2008 October 11

= October 11 =

4th grade physics question (fluids, force, pressure)
A partially evacuated airtight container has a tight fitting lid (of negligible mass) over a airtight container.


 * Surface area of the lid = 77 meters-squared
 * Pressure above the lid = 100,000 Pa
 * Pressure below the lid = unknown
 * Force required to move the lid up = 480 N

My book gives the wrong answer (38,000 Pa), I just need a verification that its 99,993 Pa, or am I just using a wrong measurement such as meters instead of millimeters. Thanks, i'm embarassed to even ask this question, its easy algebra. The only reason I ask, is that I missed the first 4 questions in a row before this question (all for careless mistakes) but this one is playing tricks on my mind. 38kPa is the correct answer if the conversion factor between a netwon per square meter and a Pascal was some other amount. This was from yesterday's 11th hour of a study session and it caused me a great deal of headache, and I look forward to starting today's marathon session with closure. Sentriclecub (talk) 10:25, 11 October 2008 (UTC)
 * Are you sure you have the question right? The given answer is right if the surface area is 77 square centimetres (which is also a much more reasonable size for an airtight container!). Algebraist 10:57, 11 October 2008 (UTC)
 * Thanks. I'm looking at the book right now Fundamentals of Physics 8E Jearl Walker and I bought the detailed solutions manual. Now I can have my sanity back. Sentriclecub (talk) 11:09, 11 October 2008 (UTC)