To answer your question, I think it's best to describe the car as a free body floating in space. We engineers have been taught to think of objects as free-bodies in space with mass acted on by forces with a net value on the various linear and rotational axes. When a force acts through the center of a body of mass, like a pool ball, it causes linear motion. When it acts upon a body of mass such that the force vector does not pass through the center of mass, rotation and motion occur.

A simple free body diagram for a car could look like this:


In the 'Y' direction we have the center of mass (CM), and the 2 reaction (R) forces at play at the tires. Sum the reaction forces and it will equal the weight of the car. Multiply these reaction forces by the coefficient of friction and you have the maximum available force for acceleration.

Once we rotate the drive axles, the diameter of the drive tires from the axle to contact patch on the pavement (a lever-arm on a rolling object) can be factored in to determine the force which pushes backwards at the track (F1 to the left) in order to propel the car forward (F1 to the right).

Sooner or later, all the complex factors involved here, the interaction of the chaisis to the suspension to the drive axel's, the deflection of the tire's sidewall, the aerodynamic drag, the friction of mechanical parts sliding against each other on hydrodynamic oil films, etc all could be sumed to resultant vectors about the 6 axis's (XYZ, and rotation with respect to those axis's) and ultimatly applied to the center of mass.

 

I might get some flak for saying this, but as far as when the most acceleration for any mass occurs, it is during the infinitesimally (spelling?) small period of time in which the car changes from stationary to moving. If I'm wrong, the engineers and such of this discussion please correct me and tell me where I'm wrong and why. It's only a self-arrived to conclusion of my own I've had for some time and now I have the chance to see if I'm correct or not, as well it applies to the discussion.

 

thanks to shadowboy and power2weight. both your posts cleared up a lot for me. i think the literal answer to my question is found here:

ilaureliusli - THAT is an interesting question to ponder. obviously the velocity would be infinitely greater at that instant than it was in an instant prior. would then the acceleration at that moment be infinitely large as well? the car's entire potential energy would be instantaneously transformed to kinetic energy...

truthfully, i don't know the answer to your question. it makes sense, but... my mind keeps jumping to calculus (which sadly i can remember very little of). can anyone clarify?

 

Actually the greatest acceleration any car will have will be in the lowest gear at max torque, assuming there is no wheel spin.

Depending on the clutch slippage and gearing that could be between 0 and 1 MPH or at 20 mph.

So in other words, it depends.

 

Assuming of course you throw out the "launch" a car gets from shocking the drivetrain and hooking well on the starting line.

 

some of these replies are funny. i understand that torque and HP are like apples and oranges. they are nothing alike. one is a mathematical formula and one is a type of force that is applied.

torque is the amount of rotational force that an object can develop.

horsepower is a function of torque over time and distance. the actual formula for horsepower is 33,000lb-ft/1 minute this is a formula that James Watt derived. FYI, 1HP = 745.699 watts.

hp is the amount of energy created and quantified in different units. torque is a type of work that is performed. energy is required to do work. work creates energy. to figure out how much energy is created by doing work, you divide the work by time. this gives you how many units of energy are created when performing work over time.

thats what horsepower and torque ARE... what they DO and what they FEEL like and how you RELATE to them is geographically, culturally and demographically unique. just look at a 20 year olds explanation and the 40 year old's explanation.

"Horsepower sells cars, Torque wins races!"

 

lol^

 

lolol^

 

some one ban this faggot