Comments on: JLP’s Roundup – April 11, 2008

By: Bryce

Bryce — Mon, 14 Apr 2008 07:40:30 +0000

You are correct that it takes more energy to go faster over the same distance and that’s roughly why it takes more gas to drive faster. If you want to get technical, the power to overcome aerodynamic drag is proportional to the cube of velocity.

Lumping a bunch of constants based on the frontal area and drag coefficient of the vehicle along with density of the air, you get an equation like P = C * v^3, where P is power and v is velocity. If you know that it takes a certain amount of power to move at a particular velocity you can solve for C. Then you can solve for P at any other velocity.

Example: if it takes 20 horsepower to drive at 50 mph, C = 20/50^3 = 0.00016. Then the power required to drive at 75 mph is P = 0.00016*75^3 = 67.5 hp.

This has been known since Lord Rayleigh derived it at Cambridge in the 1870s.

And yes, I’ve left out frictional loss.

So, now you’re prepared for the next time someone asks.

P.S. I like your blog’s new look.

By: Tricia

Tricia — Sun, 13 Apr 2008 23:13:52 +0000

You are right JLP, we can start to taste it now. Thanks for the mention

By: Ron@TheWisdomJournal

Ron@TheWisdomJournal — Sat, 12 Apr 2008 01:37:54 +0000

@ Glblguy
LOL! Some people just have no common sense.

By: Glblguy

Glblguy — Fri, 11 Apr 2008 23:18:44 +0000

Glblguy says: “Thanks JLP, but I just don’t think you or your mouth are a good fit for this position.” He then reaches down and presses the eject button.

Glblguy: “Next!”

Seriously, thanks for the inclusion. Had a guy the other day tell me, after we told him about some cool stuff we were doing “That’s f-in awesome man”.

By: Flexo

Flexo — Fri, 11 Apr 2008 17:49:05 +0000

Thanks for the mention, JLP. When it comes to frugality, balance is the key IMO.

By: Ron@TheWisdomJournal

Ron@TheWisdomJournal — Fri, 11 Apr 2008 15:56:10 +0000

Thanks for the link JLP!
Hope you enjoy the weekend!