Let's take a look at the physics of the weight system. (What is the purpose...)
By adding weight you increase the force required to accelerate and decelerate the mouse according to F=MA, or Force = Mass x Acceleration, from Newton's Second Law. If the mouse has more mass, your hand has to work harder to move it. For the purposes of this article, we'll assume that half of any given mouse movement is acceleration and the other half is deceleration. So you're working harder to start the motion and stop the motion.
Momentum takes place in between acceleration and deceleration. Momentum is stated as P=MV or Momentum = Mass x Velocity, again from Mr. Newton. What this says is that when something of a given mass is moving at some velocity, it's going to take an equal amount of mass and velocity in the opposite direction to stop it. A basic example is Car vs Minivan, head-on, both travelling at the same speed, in a test lab. The net reaction after the impact will be a slower speed in the direction the minivan was going for both vehicles because the minivan had a higher mass. (We'll ignore the fact that the vehicles deform in an impact for the purposes of this explanation.) What does this mean for the mouse? After it accelerates, it now has momentum and requires your hand to provide an opposite momentum to counter its movement.
There are three parts of this system, the mouse your hand and the mouse pad or other such tracking surface. Mouse makers usually try to make the friction between the mouse and the pad as low as possible so it's only your hand interacting with the mouse. Practically we'll ignore the friction between the mouse and the pad, mathematically there is some resistance.
For the mouse:
- Logitch G502 Mouse weight (empty): 121 grams (excluding the
- Total G502 weights: 5 x 3.6 grams, or 18 grams
- Total G502 and weights: 139 grams
- Max G502 speed: >300 inches per second (>7.62 meters per second)
So if you add all the weights you can increase the mouses mass by about 15% (in approximately 3% increments).
For a hand:
For these next assumptions, we'll use all metric to avoid confusion. You make a quick 90º turn in your FPS - moving your mouse 2.5 cm (about 1 inch) in 0.1 seconds. An acceleration and deceleration of 5 m/s/s. For a fully loaded mouse, that's 0.695 N - empty it's 0.605 N. Can you hand take that? 55 N >> 0.7 N. But what does the difference between empty and fully loaded really feel like? The "real" answer is 18 grams. The practical answer is about the force it takes to turn a slightly-less-than-ideally fitting nut onto a correctly sized bolt - not very much.
What about momentum? An average human hand weights about 0.58% of their total body, so for 140 lb person (about 63 kg), that's about 0.365 kg for a hand. This is 3.8 times more than our fully loaded mouse, or 3.3 times for the empty version.
So when your hand decides to "collide" with your mouse, I'm pretty sure your hand is going to win. But what does this mean to me? (How do I use them correctly?) That's really up to the perception of each person. By changing the weight you're changing the "balance of power" between your hand and the mouse. I can suggest that you "bounce" your mouse back and forth between your thumb and pinky quickly with various weights and see if you a) notice a difference, b) if you do, tune it to what you like. People with a stronger "grip" or general hand/arm strength may find that a lighter mouse may move too much when performing quick movements. As to "How do I arrange my weights?" While technically, the placements of the weights in the mouse affects its center of mass, which affect how it moves when your grip interacts with it - practically it really doesn't matter. The individual weights are so small compared to the overall weight of the mouse, AND, you're moving the mouse as a whole, AND generally the whole mouse is moving in and with your hand, you'll never notice. Unless... (just for the few of you where it does matter), you move your mouse by using only two fingers, in which case, ideally, you want all of the mouses mass concentrated between the "squeeze points" of your fingers - otherwise you get unwanted rotation when you try and translate the mouse on the pad.
To answer a four year old question... :P