1. Free Body Diagrams and Newton’s Laws

2. Free Body Diagram
A diagram of all the external forces on an object. The object is drawn as is floating in space (“free”).
Only include forces on the diagram, not other vectors such as acceleration or velocity.
Only include the actual individual forces, not components or net forces.

4. Example
Ftable
Free Body Diagram Fg

5. Object or System of Objects

6. Problem #1
A 55 N box is at rest on a table. What is the force of the table on the box?

7. Ftable Fg

8. Problem #2
A 20 kg box is at rest on a table. What is the force of the table on the box?

9. Ftable Fg

10. Problem #3
Two 20 kg boxes are tied together with a rope. A force of 40 N is applied to the block on the right. What is the acceleration of the blocks?

11. Treating the boxes as one system

12. Problem #4
Two 20 kg boxes are tied together with a rope. A force of 40 N is applied to the block on the right. What is the tension in the rope?

13. Examine the forces on one box

14. Problem #5
Two 20 kg boxes are tied together with a rope. A force of 60 N is applied to the block on the right at an angle of 30 degrees to the horizontal. What is the acceleration of the blocks?

15. Treating the boxes as one system

16. Problem #6
The length of the chain between the car and the tree is 15.0 m and the perpendicular force causes the chain to deflect 0.5 m from the dotted line in the diagram. If the perpendicular force is 100 N what is the force T on the car if the car doesn’t move?

17. Examine the point in the chain where the perpendicular force is applied