[quote=“RedrRocket,post:478,topic:26320"”]
im not trying to start anything.
[/quote]
Me neither. If anything, this is the kind of discussion an automotive forum should have more of.
[quote=“RedrRocket,post:478,topic:26320"”]
" * There’s no coasting in racing! You should always be on the throttle or on the brakes. And you should be on the brakes as little as possible.
* Keep it smooth. Braking smoothly keeps the car settled. Slamming on the brakes unsettles the car, risks lock-up, and is less effective.
[SIZE=3]* Brake as hard as you can, and as late as you can, without locking up your brakes.[/SIZE]
… blah blah, lots more good info about the best way to go fast
[/quote]
I know that maxium braking is best for LAP TIMES. Hence the reason I was braking as late as possible and as hard as possible, up until my brakes overheated. It goes back to using 100% of your traction. To be as fast as possible you want to use all your traction all the time. If you’re in a corner, 100% should be turning. If you give 100% traction to turning and you find you’re cutting to the inside, it means you’ve got some traction to spare that you could be using for going faster. etc etc, it gets a little more complicated, but that’s the general idea. Same thing with braking. If you’re going in a straight line and you’re only using 50% of your available traction to stop, you’re wasting 50% of your traction. You should have been using it to accelerate, and then used 100% of your traction to stop later.
But that only works if your “race car” is capable of giving you 100% lap after lap.
Which brings us back to:
[quote=“RedrRocket,post:478,topic:26320"”]
We all know it takes the same amount of force to stop a moving object when its moving.
but if that force is applied strongly within a short amount of time it should generate lest heat from friction than using the same amount of force spread out for a longer duration of time.
im not a physics major, nor an engineer. someone help me out, correct me if im wrong.
[/quote]
Nope, you have it backwards. Think of it in terms of acceleration first. To accelerate my pig of a car to 60 mph in 4.8 seconds, it takes 400 HP. HP is just a measure of force, specifically the ability to lift 33000lbs one foot in one minute (thank you Mr James Watts). 400 HP is the force acting on the car to change it’s state from motionless, to 60 MPH. With 200 HP it would never reach 60 MPH in 4.8 seconds, because you’re only putting 200 HP worth of force into the equation.
So once you’ve put all this HP into the fat pig of a car to get it to reach 60 MPH, it carries a certain amount of kinetic energy. I’m probably going to screw up the math, but you’ll get the idea.
60mph = 26.8 Meters/Second
3800 lbs = 1723 Kilograms
Kinetic energy = 1/2 (M * (V * V)), or 618763.76 Joules.
So the fat pig of a GTO has 618763.76 Joules of energy simply “existing” at 60 MPH. Since energy can be neither created nor destroyed, the brakes have to disapate this energy in order to bring the car back down to zero meters/second.
Kinetic energy is the energy of a moving object, and is dependent on the mass of the object and the velocity at which it is traveling. Heavier objects and faster moving objects have more kinetic energy — that is to say, a semi-truck traveling at highway speeds has more kinetic energy than a baby carriage traveling at walking speed. You could stop a baby carriage with your hand, but a semi-truck would barely slow down at all as it ran you over because it has a lot more energy. Kinetic energy is the energy required to bring an object up to a velocity, or to stop the object which is traveling at that velocity.
So, it will take more kinetic energy to decelerate in less distance than it would to decelerate in more distance. Same as it would take more kinetic energy to accelerate in less distance. More energy being disapated by brakes = more heat, since brakes basically do nothing but convert kinetic energy to heat. It doesn’t matter than you’re on the brakes for less time because you’re forcing them to do much more work.
Remove the brakes from this and think of it another way. You’re running with a wheelbarrow full of rocks that weighs about 150 pounds. You’re running just as fast as you can. Which will require more effort on your part.
- Stopping the wheelbarrow in 2 feet.
- Stopping the wheelbarrow in 20 feet.
Yep, you’ll need to put much more energy into stopping in 2 feet than you would in stopping in 20 feet. If there was a brake on that wheelbarrow, it would still be following the same physics laws.
[quote=“OriginalSterm,post:479,topic:26320"”]
Ever coast down a long hill, constantly applying the brakes and not allowing them to cool, then try and stop the car quickly at the bottom? How well did they work?
[/quote]
Terrible example in this case, because you’re introducing a new force and not accounting for it… GRAVITY.
Instead of riding your brakes all the way down, lets assume you don’t touch the brakes at all, or use engine braking, and you remove the friction from the air that would slow your car down as the speed increased. At the bottom of the hill your car would be going 1000 mph or so, and if you stood on your brakes to the point of ABS engagement they would fail MUCH MUCH MUCH worse than had you simply rode them all the way down.
We really need BikerFry to get back from his damn honeymoon and school us with his engineering skills. My software engineering isn’t helping me here, and it’s been a while since I was in school and worked with these formulas.