Life's a drag

[Propellor]

http://www.wallaceracing.com/Calculate%20HP%20For%20Speed.php

They want an input for weight.

Putting vastly different weight figures into their calculator doesn't affect required hp much at all, so I think they are estimating the difference in rolling resistance. In that case I'm sticking to my guns! 

Interesting to put some figures in though and watch how the power required changes alarmingly as the speed goes up. It also shows how little power is needed to reach the legal limit, with a, low drag coefficient and a small frontal area.

[Oldtimer]

Now we are getting into the realms of perpetual motion.

[Propellor]

Now we are getting into the realms of perpetual motion.

How so?

I don't get what you mean.

[timbo]

One day I will sit down and read all five pages of this thread, one day 

[tommy]

yes its on my bucket list too,   

[guest295]

I watched a couple of guys in superkarts lap the Pukekohe Racecourse several seconds faster than anyone had before. The previous tryers were in F5000 cars, F1 cars, GP bikes, you name it. Superkarts are long karts with very slippery bodywork in which the driver is more or less lying down with only his eyes visible. The engine is a water-cooled 250 2-stroke producing maybe 100 hp. The whole thing weighs pretty much nothing and has hardly any frontal area.

That probably contributes nothing to the discussion but the karts sounded wonderful.

[Propellor]

I watched a couple of guys in superkarts lap the Pukekohe Racecourse several seconds faster than anyone had before. The previous tryers were in F5000 cars, F1 cars, GP bikes, you name it. Superkarts are long karts with very slippery bodywork in which the driver is more or less lying down with only his eyes visible. The engine is a water-cooled 250 2-stroke producing maybe 100 hp. The whole thing weighs pretty much nothing and has hardly any frontal area.

That probably contributes nothing to the discussion but the karts sounded wonderful.

I once saw a super kart of the day back in the late seventies race Ron Haslam around Silverstone. The kart would have had an air cooled yam twin I guess. It was just Ron on a bike against the kart, prior to the main race meeting. I think the kart won from memory.

[Propellor]

I'm not sure I see zeno's stadium paradox as a paradox. I think I can accept it at face value. It seems ok to me to be able to cover unequal distances at the same time. You can choose which object you want to declare as your frame of reference surely? And have more than one going on at the same time. It happens all the time doesn't it?

The one thing wrong with it, in my eyes, is that it deals with straight line parallels. I'm not sure they exist. Anywhere.

Dunno. I'm probably wrong.   

[Propellor]

It's hard to believe, looking at the footage, that the ISS is travelling at 17,000 mph. Or that the value of gravity is 90% of what it is on earth's surface.

A drag related thought: when a space rocket headed for the ISS takes off, once it has enough thrust to overcome gravity, is it in its interest to accelerate as slowly or as quickly as possible?

[Propellor]

I think you would have to compare a motorcycle and car of the same weight for the comparison of the effect of drag to be meaningful between the two. 

Read a posting on bike EXIF with a lovely engineered BMW Landspeeder custom. There's a comment by the guy regarding the effect of weight on top speed. Sorry, but I couldn't help thinking of the discussion on this thread. 

http://www.bikeexif.com/bmw-landspeeder