How Do You Calculate Recoil Speed in Ballistics?

[Ki-nana18]

A bullet with mass 0.40 kg is fired with an initial velocity of 400 m/s from a gun with mass 5.0 kg. The speed of the recoil of the gun is?

Do I use this equation m₁v₁=m₂v₂?
Can someone give me just a hint?

 

[rock.freak667]

Yes you would need to use conservation of linear momentum.