Okay thank you for explaining that. I'm sorry that this is your question and I'm not being completely helpful. Hopefully someone can confirm this though.
Okay, you're probably right about us not being able to bring the ground into this. Okay so now I am wondering why the force of the box pushing down on the cart can't be weight? What force would that be if it can't be weight?
Hi,
I am actually working on this problem too. I can't tell for sure if you're right, but I think your first one adds up because it's acting on 2 different objects and it's in the opposite direction. For the second one, I was just wondering where the pulling force is supposed to come in? Could...