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[stonemonkey]

If anyone else is interested in finding out a bit more about this though, here's an article on it.

http://mb-soft.com/public2/car.html

all you need to read from this lecture is this quote

People generally talk about HORSEPOWER rather than Thrust with vehicles, but Thrust is generally described for aircraft and watercraft.

That implies that while it's more convenient to use HP in this case, a car still generates thrust.

What about:

Another side note: There is a limit to how much Thrust one can apply with tires. There is a static coefficient of friction which depends on the type of road surface, rain, snow, tire temperature, and other things.

Which is the actual accelerating force of the car.

[stonemonkey]

There's no need to call anyone a moron. But anyway, like stonemonkey says, that flying car is no longer accelerating forward, despite the engine producing torque.

What i say about the earth's mass not being part of the car system is that its force can be considered infinite related to the friction able to be produced by the tires. So generally, you can 'cut' the system off at the friction force which is ussually available through empirical data (ie testing). This is why you see tire and track temp and tire wear is always measured.

In the case of a jet, the equivalent is air. A jet wouldnt be able to produce thrust without air, in fact the jet's thrust reduces as air density lessens (like the trolley example).

But the mass of air is being considered when you are calculating a jet's thrust; while the earth's mass isnt, when you are calculating a car's thrust... That's why i was disagreeing with stonemonkey, but what he is saying is right.

Thankyou for taking the time to understand what I've been trying to say f1ea.

[bud]

That implies that while it's more convenient to use HP in this case, a car still generates thrust.
.

I prefer KW over HP when measuring a cars power. But again its not more convenient you could say its the industry standard. when you get your car tuned on the dyno they dont give you a read out of thrust, its KW and Torque. So while your argument makes you sound all professor like its not used in the real world of automobiles.

[f1ea]

I prefer KW over HP when measuring a cars power. But again its not more convenient you could say its the industry standard. when you get your car tuned on the dyno they dont give you a read out of thrust, its KW and Torque.

Both are the same, its just the unit that's different. KW and HP are both measuring power.

The reason car tuners use Torque or Power to see which car is more powerful is because, the car with the most power is potentially faster, depending on the tires and track surface. Which means more or less, in equal conditions, the car with the highest power will generate the most acceleration.

[bud]

I prefer KW over HP when measuring a cars power. But again its not more convenient you could say its the industry standard. when you get your car tuned on the dyno they dont give you a read out of thrust, its KW and Torque.

Both are the same, its just the unit that's different. KW and HP are both measuring power.
.

yes i know....

[f1ea]

yes i know....

i thought so, just making sure

By the way, i prefer HP too. Although, to measure electric energy i'd rather use KW... in fact my whole country is kinda weird regarding units... we use Feet and pounds to measure people, but use Kg and m in physics problems. Hp for cars, and W for electricity. Also, use gallons for gasoline, lbs for weight but Km/h and m for road stuff....

[stonemonkey]

its not used in the real world of automobiles.

I disagree with that, especially in F1. An f1 car can easily spin it's wheels at lower speeds meaning the power the engine produces is in excess of what is required to give maximum acceleration, the important factor is the maximum force the tyres can exert on the tarmac before they start slipping, many things can affect the value of that maximum force, downforce, suspension, tyre/track temp etc. So I would think that maximizing that force is quite important to the F1 engineers, especially the Mclaren engineers atm.

[bud]

yes i know....

i thought so, just making sure

By the way, i prefer HP too. Although, to measure electric energy i'd rather use KW... in fact my whole country is kinda weird regarding units... we use Feet and pounds to measure people, but use Kg and m in physics problems. Hp for cars, and W for electricity. Also, use gallons for gasoline, lbs for weight but Km/h and m for road stuff....

That is weird! We are all Metric here makes things easier.

[Gaz]

You accepted earlier that throwing bricks out of a shopping trolly was in some wierd way a form of thrust, it's not wierd at all, it's exactly the same principle as how rockets work. In the case of most rockets the propellant is the energy source but not always, for example the ion rocket which uses electric charge to accelerate the propellant the fuel source being some type of electric cell and in the case of the shopping trolly, the brick is the propellant and the fuel source is the food you ate to give you the energy to throw it.

Yeh because thats you ejecting the mass creating an equal and opposite reaction.

You would have to have alot of mass tho ejecting at a high verlocity.


With the car sitting on a trolly, you accept that if the trolly has more mass than the car the car will accelerate more in one direction than the trolly will in the other.

and also that if the car has the greater mass then the trolly will accelerate more in one direction than the car will in the other direction. If they have equal mass then the acceleration of both will be equal but in opposite directions.


No i said if the trolly weighs less than the car the car will remain stationary but throw the trolly from underneath it.

And if the trolly has more mass than the car it will just roll off it with the trolly remaning stationary.

Of course there's bits inbetween where the car moves slightly forward and the trolly is pushed away.




The force accelerating the trolly is the force that the tyres of the car exert on the trolly and the force accelerating the car is the force the trolly exerts on the tyres which is thrust, the mass of the trolly being the cars propellant which will be the case even if the trolly has the mass of a planet.

That is all accepted physics.

the fact is thats not thrust because the trolly is just either making the car remain stationary or move more slowly forward than if it was sat on the ground. the car forward momentum is provided by the engine and tires not any mass being ejected.

In a car what Mass is being expelled to create thrust?

[stonemonkey]

The mass being forced in the opposite direction is the trollys mass, It doesn't matter if the mass is solid,liquid or gas or comes from within the vehicle or not, a jet engine sucks in air and acceleratess it out the back at a high velocity .The force exerted between the tyres and the trolly force the trolly to accelerate in one direction and the car to accelerate in the opposite direction, they push each other in opposite directions. In the case of a car on the ground it's the earths mass but as f1ea said, the eaths mass is so big compared to the mass of a car that there will be very little effect on it and is usually ignored.

[bud]

stone monkey, thrust for a glider?

[Gaz]

The mass being forced in the opposite direction is the trollys mass, It doesn't matter if the mass is solid,liquid or gas or comes from within the vehicle or not, a jet engine sucks in air and acceleratess it out the back at a high velocity .The force exerted between the tyres and the trolly force the trolly to accelerate in one direction and the car to accelerate in the opposite direction, they push each other in opposite directions. In the case of a car on the ground it's the earths mass but as f1ea said, the eaths mass is so big compared to the mass of a car that there will be very little effect on it and is usually ignored.

The Earth is not being expelled or accelerated.

its just stationary.

[bud]

The mass being forced in the opposite direction is the trollys mass, It doesn't matter if the mass is solid,liquid or gas or comes from within the vehicle or not, a jet engine sucks in air and acceleratess it out the back at a high velocity .The force exerted between the tyres and the trolly force the trolly to accelerate in one direction and the car to accelerate in the opposite direction, they push each other in opposite directions. In the case of a car on the ground it's the earths mass but as f1ea said, the eaths mass is so big compared to the mass of a car that there will be very little effect on it and is usually ignored.

The Earth is not being expelled or accelerated.

its just stationary.

the earth is not stationary

[Gaz]

The mass being forced in the opposite direction is the trollys mass, It doesn't matter if the mass is solid,liquid or gas or comes from within the vehicle or not, a jet engine sucks in air and acceleratess it out the back at a high velocity .The force exerted between the tyres and the trolly force the trolly to accelerate in one direction and the car to accelerate in the opposite direction, they push each other in opposite directions. In the case of a car on the ground it's the earths mass but as f1ea said, the eaths mass is so big compared to the mass of a car that there will be very little effect on it and is usually ignored.

The Earth is not being expelled or accelerated.

its just stationary.

the earth is not stationary

LoL Yes but last time i checked when i did a fast start in my focus the earth didn't start spinning the other way.

So its stationary relative to the car.

[stonemonkey]

stone monkey, thrust for a glider?

That's well off topic. But anyway, I assume you know how wings and the control surfaces of aircraft work. Other than that the physics of a glider is pretty much the same as the physics for a rollercoaster, instead of a chain pulling it up to the top of the first hill to increase it's potential energy a glider uses thermal currents.
On the thrust, not sure if it's still considered thrust but it's the gravitational force between the glider and the earth that accelerates the glider (and the earth) towards each other. The masses are being accelerated in opposite directions, just in this case they're pulling toward each other instead of pushing away from each other.

Do you realise that when you lift a weight above your head that you're actually pushing the mass of the earth and the mass of the weight apart? With the earths mass being so much greater than the weight you are lifting the earth will only move a very very tiny amount compared to how much the weight moves.