# Angular mama mia!

1. Jan 9, 2004

### Thallium

What is angular momentum? And what is momentum in general? This term appears all the time on this board and I dare not try the search engine to find an explanation. I have tried, but I understand none.
Please, if there are any foreign words in your explanations, explain them too.

2. Jan 9, 2004

### Njorl

There are two things to know about - linear momentum and angular momentum.

Linear momentum is usually just called momentum. Mathematically, it is the product of an object's mass and velocity. It is usually represented by the letter "p", as in p=mv. Qualitatively, it is hard to describe. It is a capacity to keep going I suppose, but that is not very satisfying.

Angular momentum, usually represented by "L" is a bit more complicated. It relates mostly to spinning things. Consider a kid whiling a rock around on the end of a string in a big circle. The angular momentum would be a product of the mass of the rock, the length of the string and the angular velocity (degrees per second) of the whirling. The angular momentum of more comlicated objects is determined by assuming that they are made up of an infinite number of infinitesmal whirling bits.

Momentum is interesting, because, in a closed system it is conserved. When 2 things collide, they may change speeds, but the total momentum of the system will stay the same.

Njorl