Solving Two Body Problems - The Physics Classroom

[RiskX]

Hi,

I'm currently learning how to solve two body problems and I'm having a little trouble with that. My question regards a certain example I found in The Physics Classroom website that goes like this:

"A 5.0-kg and a 10.0-kg box are touching each other. A 45.0-N horizontal force is applied to the 5.0-kg box in order to accelerate both boxes across the floor. Ignore friction forces and determine the acceleration of the boxes and the force acting between the boxes."

I managed to find out the acceleration(3 m/s/s) but I don't understand how to find the force acting between the boxes. In the solution of this example they took the 10 kg boy and just calculated it's net force(30 N) and I undertood that but if I to calculate the net force acting on the 5 kg(15 N) body I'll get a different result entirly.

How can I determine the force acting between the boxes using the 5 kg box alone.

Thanks!

 

[Spinnor]

See the attached,

 

[RiskX]

I'm sorry but I bealive you forgot the attachment...

 

[Spinnor]

Right, sorry %^) And I normally preview stuff.