tag:blogger.com,1999:blog-7327817.post115204644433315016..comments2024-01-25T13:55:08.273+00:00Comments on Gendal World: Where's a physicist when you need one?Richard Brownhttp://www.blogger.com/profile/14808940497740675782noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-7327817.post-1152283617774947552006-07-07T15:46:00.000+01:002006-07-07T15:46:00.000+01:00GENIUS!!GENIUS!!Richard Brownhttps://www.blogger.com/profile/14808940497740675782noreply@blogger.comtag:blogger.com,1999:blog-7327817.post-1152207484447877992006-07-06T18:38:00.000+01:002006-07-06T18:38:00.000+01:00Grr, I thought you might ask me that. How do you ...Grr, I thought you might ask me that. How do you expect me to do maths in a text box that doesn't even let me do superscripts? You'll have to grab it <A HREF="http://umcus.org/~benc/fanspeed.pdf" REL="nofollow">here</A>.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7327817.post-1152173534317267032006-07-06T09:12:00.000+01:002006-07-06T09:12:00.000+01:00The fan was going fast enough that the bladed were...The fan was going fast enough that the bladed were blurry. 2-3 revolutions per second sounds entirely reasonable.<BR/><BR/>Could you show your working please? :-pRichard Brownhttps://www.blogger.com/profile/14808940497740675782noreply@blogger.comtag:blogger.com,1999:blog-7327817.post-1152122369091966592006-07-05T18:59:00.000+01:002006-07-05T18:59:00.000+01:00How about using conservation of energy and momentu...How about using conservation of energy and momentum? We could make the very dodgy assumptions that all the momentum from the blades is given to the air, creating a cylinder of air moving uniformly at 3/4 m/s perpendicular to the fan.<BR/><BR/>I think this leads to an angular velocity of w = 9/16r rad/s, where r is the length of the blades (and the radius of the cylinder). Then if r = 0.25 m, we get w = 2.25 rad/s, i.e. about 2.8 revolutions per second. Presumably losses in practice would mean the fan was actually going a bit faster.<BR/><BR/>Do you see how fast the fan was actually going?Anonymousnoreply@blogger.com