How much momentum does a moving object have

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

Acertain radio station broadcasts radio waves that have a wavelength of 298cm what is its broadcast frequency?

Explain why you think this diagram shows what happened to the carbon in the biodome.