Car shuts off at 98!!!!!

[jstreet0204]

It sounds as if what you are proposing is that if I floor my car and run it up to say 80 mph and let of it will immediatly stop accelerating at that speed and not go one bit faster. Or if I get to that speed and push the clutch in it will immediatly start to slow down..

That is exactly what I am saying. The car will not continue to accelerate without force. It may not feel like it, but momentum will only keep it at its current velocity.

That is absurd and I suggest you go out and try it before you tell me "Newton's laws say it ain't happenin".

In physics, momentum is the product of the mass and velocity of an object. If it's gaining velocity at a rapid rate, even taking power away, it will for a short time continue to have momentum. And given the mass of the object it can still gain speed until friction over takes the available stored energy and starts to slow it down.

You are confused.
The definition of acceleration is change in velocity.
momentum keeps a body at its current velocity period. force is required to change the velocity positively or negatively.

 

[DaNd4Speed]

It sounds as if what you are proposing is that if I floor my car and run it up to say 80 mph and let of it will immediatly stop accelerating at that speed and not go one bit faster. Or if I get to that speed and push the clutch in it will immediatly start to slow down.

That is absurd and I suggest you go out and try it before you tell me "Newton's laws say it ain't happenin".

In physics, momentum is the product of the mass and velocity of an object. If it's gaining velocity at a rapid rate, even taking power away, it will for a short time continue to have momentum. And given the mass of the object it can still gain speed until friction over takes the available stored energy and starts to slow it down.

But you're missing one thing...that stored energy is not increasing once you remove an additional force (In this case the gas pedal). Momentum is the residual force and will not increase unless there is further input of force greater than what is already applied. If that was the case we would have had hybrid technology long before the Prius and Insight, we could simply use that energy to power our cars and get better gas mileage.

Think of it this way. Spin a top, you spin it as fast as you can then let it go on the floor, is it spinning faster at any point once you release it? You have stored energy until the forces of friction completely bring it to a stop.

The only scenerio that acceleration could be happening once you let off the gas is as follows:

1) Going downhill
2) Lag of throttle response
3) Idle set way too high.

 

[jstreet0204]

Take a 10" diameter 1" thick "wheel" of steel. Accerate it at a constantly rising rate and then abruptly take away the accelerating force. For a short time the wheel will continue to accerate due to it's mass.

Ummm no, it won't.

 

[tjm73]

Ummm no, it won't.

Ummm yes, it will.

I'm done with this as it is a waste of my time.

 

[skrowdilos]

Uhhh, a body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an external force.

TMJ, I don't know where you learned physics, but you might want try again.

constant, not accelerating. Unless acted upon.

 

[tjm73]

Well I say again....

Then please explain to me how my car continues to gain speed even after I have removed engine forces by depressing my clutch, disconecting forward motion providing power.

When I push the clutch in at 70 mph while accelerating hard, the car continues to gain some speed, all be it at a slower rate of gain and it continues to slowing rate. Yet it is still gaining speed. An additional 5-10mph is the norm.

And this is on flat, level ground.

 

[Kilgore Trout]

^ tail wind

 

[DaNd4Speed]

Well I say again....

Then please explain to me how my car continues to gain speed even after I have removed engine forces by depressing my clutch, disconecting forward motion providing power.

When I push the clutch in at 70 mph while accelerating hard, the car continues to gain some speed, all be it at a slower rate of gain and it continues to slowing rate. Yet it is still gaining speed. An additional 5-10mph is the norm.

And this is on flat, level ground.

We can't explain to you how it gains speed because IT CANT!!! Good lord, I'm a Mechanical Engineer cryin out loud! Please by all means drive from Rochester down state and stop on by to show me your special car and I'll install a Flux Capacitor for you!

 

[tjm73]

We can't explain to you how it gains speed because IT CANT!!!

Then explain what other forces are causing the car to continue to gain some speed. Everyone is quick to discount my ideas, but no one has offered any other explainations.

 

[jstreet0204]

Then explain what other forces are causing the car to continue to gain some speed. Everyone is quick to discount my ideas, but no one has offered any other explainations.

I would look for a simpler explanation like the momentum of the speedo needle as opposed to the continued acceleration of the car.

 

[CanadaStang]

Actually this ability to continue gaining speed even after letting off is enhanced with an automatic. They, by design, store energy in the fliud within them and then distribute that energy in, for lack of a better term, a smoother way. Ever hit the gas in grandma's car and nothing happen's for a second or two? Well something is happening. Energy is being stored and it will be delivered even if you let off.

With a stick the engine is pysically connected to the transmission via the clutch as long as the clutch is engaged. When you let off, the engine adds a large ammount of immediate force slowing the car.

The car will continue to accerate until frictional forces overcome the stored energy and then the car will stop accerating completly and start to slow down.

If you've ever hit the speed limiter in an auto, you'll know what I mean. There's no "slingshoting" any faster. When speeds get up 100mph there is alot of resistance from the wind, and as soon as the speed limiter kicks in, you know it.

 

[skrowdilos]

Its hard to explain something that is not possible.

 

[DaNd4Speed]

Then explain what other forces are causing the car to continue to gain some speed. Everyone is quick to discount my ideas, but no one has offered any other explainations.

I did, read my prior post with the 3 conditions I listed.

Now I want YOU to tell me what additional forces there could be that would be GREATER than the force already sustained in the car to positively acclerate it? Keep in mind this force would have to be GREATER than the force previously applied to the car when your foot was on the gas.

I'm really done trying to explain this to you, I'd really hate to start using Kinematics equations, because the laymens terms you're not understanding.

 

[DBMSTNG]

Well I say again....

Then please explain to me how my car continues to gain speed even after I have removed engine forces by depressing my clutch, disconecting forward motion providing power.

When I push the clutch in at 70 mph while accelerating hard, the car continues to gain some speed, all be it at a slower rate of gain and it continues to slowing rate. Yet it is still gaining speed. An additional 5-10mph is the norm.

And this is on flat, level ground.

maybe there's a delay between actual speed and gauged speed in your car.

 

[wht03GT]

I feel smarter now.....

 

[tjm73]

I feel smarter now.....

And I'm trying to figure out WTF is going on with my car?!?!? You can't argue with physics yet my car seems to do the impossible. So something else is going on.

 

[tjm73]

Back to the original post. Another possibility is the 103mph could also be the speed measured on the track, while the 98 mph mentioned is the speed displayed on the speedometer. We all know how "accurate" the factory guages are.

 

[CanadaStang]

Back to the original post. Another possibility is the 103mph could also be the speed measured on the track, while the 98 mph mentioned is the speed displayed on the speedometer. We all know how "accurate" the factory guages are.

That's very plausible, but I also noticed he's running a 75 shot, and hitting the speed limiter when your spraying....

 

[Reimann]

And I'm trying to figure out WTF is going on with my car?!?!? You can't argue with physics yet my car seems to do the impossible. So something else is going on.

I'd say your spedometer is slow at showing the actual speed. The car accerlates faster then the needle can move so it continues to go up despite the fact that you car isn't accelerating anymore. It's playing catch up.

 

[kurst]

Don't give up tjm, Einstein disproved Newton's laws too.

Maybe the distance travelled got a little shorter, or time slowed relative to the obsever...ahhh the joys of physics.