# Angular momentum objective

1. Dec 3, 2008

### sumitmanhas

1. The problem statement, all variables and given/known data
Which of the following is an accurate statement
1) The angular momentum of a moving particle depends on the specific origin with respect to which the angular momentum is calculated.
2) If the torque acting on a particle is zero about an arbitrary origin, then the angular momentum of the particle is also zero about that origin.
3) If the speed of a particle is constant, then the angular momentum of the particle about any specific origin must also be constant.
4) Consider a planet moving in a circular orbit about a star. Even if the planet is spinning it is not possible for its total angular momentum to be zero.
5) A particle moving in a straight line with constant speed necessarily has zero angular momentum.

2. Relevant equations
conservation of angular momentum and principles

3. The attempt at a solution
i am not sure whether which one is more accurate among 3,4 , could someone lead me on this.

2. Dec 3, 2008

### Carid

Perhaps if you could give us your reasoning for each answer we can understand your difficulty. I can see some fairly firm objections to both 3 and 4.

3. Dec 3, 2008

### sumitmanhas

so for the first 1 ) this is likely to be true , which i never thought of because evrytime you calculate your angular momentum you choose the point of rotation and from there using right hand rule determine the direction (in or out)
2) makes no sense because if there is no torque acting on the origin then the angular momentum is constant
3) if speed is constant then angular momentum = mrv is same since the mass remain the same throughout
4)if an object keeps rotating doesn't it have an initial momentum and final momentum which are same , so, i mean it is constant then.
5) particle in straight line can have angular momentum , as in the case of a person jumping of the merry go round with horizontal speed doesnot have zero angular momentum.

reply as soon as possible plz

Last edited: Dec 3, 2008
4. Dec 3, 2008

### sumitmanhas

i belive the first one is more accurate....