Mathematics desk
< October 10	<< Sep \| October \| Nov >>	October 12 >

Welcome to the Wikipedia Mathematics Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

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)[reply]

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)[reply]

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)[reply]