# Homework Help: Diagram question

1. Oct 27, 2009

### sarahaha288

When making a free body diagram of a loop de loop i know that the downward force of gravity and the downward normal force are acting on it, and it is the acceleration force that works upward. But in the diagram is the acceleration force needed?

and also, in a net force diagram do you illustrate the acceleration force there? because without it then the net force would be going downward, which is obviously not that case. thanks!

2. Oct 27, 2009

### XanziBar

When you make a free body diagram just include all the individual forces. In your example include the normal force of the track on the cart traveling in the loop and the weight of the cart. You don't need net force or acceleration on a free body diagram.

After you have your forces the vector sum of those is equal to the mass times the acceleration of the object you drew the diagram for.

3. Oct 27, 2009

### sarahaha288

thanks that helps alot for the free body diagram, but for the net force diagram i will then have to vectors pointing downward for the normal and the gravitational force. So then would the net force be pointing downward as well? or do i include something about centripital acceleration in there?