# How to calculate the momentum of Pluto?

1. Dec 18, 2007

### ndirishchick

If anyone knows how to calculate the momentum of Pluto it would be great if you could let me know. I am doing a science project and do not understand parts of the project. Thanks!

2. Dec 18, 2007

### mgb_phys

Classical momentum is just mass * velocity

The orbital radius is around 5.9 billion km, period is 248years so it should be easy to work out velocity.
The mass is 1.3E22kg

3. Dec 19, 2007

### pixel01

Can we know the exact momentum of Pluto at any point in orbit? It's so eccentric.

4. Dec 19, 2007

### mgb_phys

But rather predictably so.
Momentum is conserved and a planet has rather a lot of momentum - as you would know if you have ever tried to stop one with your bare hands.

5. Dec 19, 2007

### pixel01

I just suspect the momentum of Pluto is not the same around the orbit, it may be quite different. I may have to look back at the Kepler's law.

6. Dec 19, 2007

### malawi_glenn

Angular momentum is more costumary to consider here.

But for linear momentum:
mv is consreved, where v is v_radial + v_tangential.

7. Dec 19, 2007

### D H

Staff Emeritus
The linear momentum of a planet (eg. Pluto) is not conserved. The planet follows a curved path!

Conserved quantities are linear momentum of the planet+sun system (tautologically zero in the planet+sun center of mass frame), angular momentum (gravity is a central force) and total energy (gravity is a conservative force).