# Alex collides with a a as he runs through his office. If the combined momentum of Alex and the desk was 400 kg m/s to the north before the collision, what is their combined momentum after the collision?

##### 2 Answers

#### Explanation:

According to the Law of Momentum:

"For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2." http://www.physicsclassroom.com/class/momentum/u4l2b.cfm

So if the combined momentum was 10kg m/s before the collison, it will still be 10kg m/s. Therfore, if the combined momentum of Alex and the desk was 400kg m/s before-hand, then after the collison their combined momentum is still 400kg m/s.

I hope I helped!

The combined momentum before and after the collision is

#### Explanation:

The combined momentum before and after the collision is

because of the principle of conservation of momentum. This principle applies to all closed systems.

I hope this helps,

Steve