Is there a Lua variable for an object's acceleration?

No, there isn't.
If you want to find the object's acceleration since last frame, then include the variable "self.lastVel" in the Create event. At the end of each Update cycle, add this:

That makes it so that it's a new vector and not just a pointer to the old one.
Then, whenever you need to check acceleration, just get self.Vel - self.lastVel, and the X and Y values will be X and Y acceleration respectively.

Is there a way to get this in m/s^2 accuarately? As in, when the acceleration is called for, it gets the current velocity and the velocity 1 second before?

Well, before we go any further, why do you need that?

I need to calculate the amount of force an object has. According to my Matter and Energy teacher, the equation is "Force = mass * acceleration".

Objects within CC (at least, bullets) virtually never have acceleration, only constant velocity. Thus, according to newtonian physics, they have a net force of exactly 0.

The fact is that this game is not really modeled after real-world physics. An object's velocity is almost always constant. Gravity does work using acceleration in the game (m*s^), but that's a different thing. I'm still not sure why you would need to calculate real-world force for this when you've already got values of mass and speed at your disposal.

I think you could write code to do what you want, if I am not misunderstanding.

I think this might do what you want.


EDIT: Oh, so I misunderstood the purpose. Nvm, nothing to see here.

That's basically what I posted earlier, but it doesn't work. You're making self.lastVelocity a pointer to self.Vel, meaning it just directly reads from self.Vel when you access self.lastVelocity. We want to store self.Vel's values, not access it again next frame, so use the technique I had above of setting the X and Y velocity individually.

I tried using "mass*Vel.Magniude" but the number was to high. Is there any way to measure force without acceleration?

That's the problem; you're not trying to measure force, you're trying to measure kinetic energy, which is another thing entirely. At least, from what I'm guessing about your purpose.

I'm trying to make a "rope."

I'm not really sure that the units matter as long as they're in distance/time^2. Granted, you'd need to do some scaling, but pixels/simupdates^2 should be fine.