Understanding Newton's 3rd Law: Finding Opposing Forces Between Two Boxes

[cam875]

I understand the law and can apply it to many situations except for one.

You are pulling a box weighing X kg attached by a connection which isn't loose or anything to another box weighing Y kg and you have to find out the strength of the opposing forces inbetween the boxes. Why is there opposing forces inside there, I always thought that if u are pulling the box than whatever is attracted to that matter you are pulling such as the connection and the other box is going to be pulled aslong as the force being applied is strong enough to move the mass and the attraction between all the matter is strong enough to hold together without breaking. So basically why are there opposing forces inbetween the boxes?

 

[tiny-tim]

Hi cam875!

Box X (at the back) doesn't want to move, so box Y has to pull it forwards, and box X is pulling box Y backwards

 

[cam875]

why is the box pulling the other box backwards? besides just using his law I like actually visualiziing what's happening, and I have been able to do that with every single example except for this one so far and its frustrating me lol.

 

[tiny-tim]

'cos if it wasn't there, the front box would go faster

 

[cam875]

alright makes sense now thanks.