My previous thread was closed due to spamming so I am reposting this.

Figure 11-26 shows three particles of the same mass and the same constant speed moving as indicated by the velocity vectors. Points a, b, c, and d form a square, with point e at the center. Rank the points according to the magnitude of the net angular momentum of the three-particle system when measured about the points, greatest first (use only the symbols > or =, for example a>b>c=d=e).




Okay, so angular momentum is equal to mass (radius cross product velocity). Since velocity is constant and the mass is the same, this leads only the radius or distance to compare. However, I am not quite sure how I should judge the distance of the particles. I mean what is the origin or the reference point that should use to judge these particles from?

I think you'd have to just assume the distance between a and b is equal to L, and then use a coefficient to describe the distances between your labelled points a - e and your particles.

For instance taking a as your first reference point, the particle to the left (for argument's sake I'll label them alpha, beta and gamma from left to right), alpha...

Distance alpha to a = pL

where p is a number between 0 and L.

And if you're describing the distance between gamma and c,

Distance = qL

where q is between 0 and L, but less than p.


It might get really confusing, but it's the only way I can see to approach it. I think also the question wants you to do the exercise 5 times, ie finding the angualr momentum of the system around the points a - e in turn, then rank them (if that wasn't clear already).

Gut instinct would tell me that e would probably be origin with the lowest value as everything is going around it, and would therefore have the lowest values of radii.

Good luck!

The problem was due last night and I got it wrong....but I'll try to make sense out of it regardless. Thanks Martyn.