|Tony Jones||17/11/2011 23:52:27|
283 forum posts
In 'Go with the Flow on p99 of the December issue Brian Winch writes: 'We now call on the services of Sir Isaac Newton and his theories on force and motion. If your model is flying very fast, the weigh increase in the fuel in the tank - being pushed back by the model's forward motion - is so considerable....'
Should Mr Winch call on Mr Newton to seek his advice, I suspect that he will find him a charred ember with burned out bearings from revolving at excessive rpm. But then what do you expect from someone who thinks the correct abbreviaion for carburretor is 'carby'?
|John Privett||18/11/2011 01:09:33|
6020 forum posts
|Oh dear, I wish he'd stick to writing about things he does understand. Physics is clearly not one of those. He wrote pretty-much the same thing in his column about a year or so ago too.|
|Tony Jones||18/11/2011 11:02:04|
283 forum posts
And I wish I knew how to spell carburettor.....
|Stefan Hafner||18/11/2011 11:16:30|
382 forum posts
|Do you mean carburetter ???|
|Martin Harris||18/11/2011 12:34:43|
9107 forum posts
|A carburetor (American spelling), carburettor, or carburetter (Commonwealth spelling) is a device that blends air and fuel for an internal combustion engine. It is sometimes shortened to carb in North America and the United Kingdom.|
|Tony Jones||18/11/2011 12:39:16|
283 forum posts
That's the one.
|Brian Parker||18/11/2011 14:21:28|
|538 forum posts|
Even if we can’t agree on the correct spelling for Carburetter/ Carburettor, it’s necessary to distinguish between Mass and Weight.
Consider this, If a can of fuel of mass ‘M’ is suspended on a spring balance in a true free falling aircraft the spring balance will record zero weight, the fuel is apparently weightless.
|Ben B||18/11/2011 14:44:43|
1419 forum posts
Oh dear! Bit of a mistake there eh? There's a fundamental difference between speed and acceleration.
If a plane was travelling at 99.99% of the speed of light (IE pretty fast ) but decelerating it's fuel would be all over the front of the fuel tank. Equally a plane travelling at 0.01mph but accelerating would have the fuel on the back wall as he describes.
Speed is irrelevant.
He was almost right though- Newton's theory's of momentum and inertia nicely explain the phenomenon being observed. But all momentum and inertia is relative (consider Einstein's lift for a moment).
If you want a nice example of how momentum is relative consider this situation. A r/c plane is flying into a head wind with forward speed equal to the airflow backwards (IE it is not moving forwards of backwards). If you chop the throttle the plane will slowly start accelerating backwards in the airflow. The acceleration shows that the plane had momentum relative to the airflow. However if you reached up and grabbed the plane (obviously not recommended) you would feel no "momentum". So does it have momentum or not? Answer is yes and no depending on what you compare it to
Please login to post a reply.
Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!