accereration 101

Guess I'll take a stab at this...

Acceleration of an object is a result of a constant force being applied to that object. In your example, the constant force is whatever is producing gravity (pushing or pulling, it doesn't matter). In the absence of a counteracting force, the object will continue to accelerate.

If the object is dropped from a considerable height in an atmosphere, it will accelerate until it reaches its terminal velocity, which is dependent on mass, configuration, friction, etc..

If the gravitational force was present in the absence of anything to produce a counteracting force (friction from air, solid object, rocket thrust, etc.), then the object will continue to accelerate to the upper limits of the force being applied (whatever those are).

Hope this is helpful...

You can drop an object on the sun from a light year away and it will accelerate all the way to the sun. It will gain velocity all the way. The gravity field of the sun causes this.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
Acceleration of an object is a result of a constant force being applied to that object. In your example, the constant force is whatever is producing gravity (pushing or pulling, it doesn't matter). In the absence of a counteracting force, the object will continue to accelerate.

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

If I supply a constant force to a car in neutral then after the initial acceleration it would stay at a constant velocity despite my constant supply of force.

Is this what is happening to an object in freefall - except it stops accelerating after reaching its terminal velocity due to the atmosphere?

If Earth had no atmosphere would this object eventually fall at the velocity of gravity (terminal velocity of gravity)?

Thanks

If you keep applying the force, the car will continue to accelerate.

Terminal velocity is reached when the force of gravity is counteracted by an equal but opposite force (due to air friction). Remember that acceleration due to gravity is dependent on the mass of the objects you're talking about (at least it is in the standard model). So things fall slower on the moon, faster on the sun, etc..

Is there a terminal velocity for gravity? Thats one of the $64000 questions. I certainly don't know.

Anything that perturbs the process should be left out of this. The velocity can be constant even as the acceleration is constant and so the two are not related by the equation v=at. Even so the statement works well for most applications. In a gravity field the direction of the object has an effect on it's velocity and the acceleration may or may not cause a change in velocity. Either way the force is the same and so what is then the result of the application of the force? This is an issue that applys in particle accelerators more than gravity fields but it seems it would be the same effect. Or not?

Actually, velocity is a vector quantity having both speed and direction. It is generally defined as change in position over change in time (v=dr/dt). Acceleration is change in velocity over change in time (a=dv/dt). You can't have a constant acceleration of an object or particle without a change in its velocity.