2. The Force Is with You FORCE DIAGRAMS

3. Learning Objectives The learner will interpret free- body force diagrams The learner will be able to draw force diagrams for different situations

4. Review: Newton’s 1 st Law An object in motion stays in motion in a straight line, unless acted upon by unbalanced force. A push or pull will cause object to speed up, slow down, or change direction.

5. Review: Forces are Balanced Object at Rest V = zero m/s Objects in Motion V ≠ zero m/s Stay at Rest Stay in Motion (same speed and direction) a = 0 m/s 2

6. Basically, objects just keep on doing whatever they are doing unless they are acted upon by an unbalanced force.

7. Review: Common Examples Ketchup stays in the bottom (at rest) until you bang (outside force) on the end of the bottom. A headrest in a car prevents whiplash injuries during a rear-end collision ( your head goes forward and then jerks backward).

8. Free Body Force Diagrams Are visual representation of force and object interactions Individual objects or members are isolated from their environment or system, illustrating all external forces acting upon it

9. Free Body Diagram Components Vector quantity has direction and magnitude Force A straight line push or pull acting upon an object Direction is illustrated by arrowhead Magnitude is illustrated by length of line segment

10. Free Body Diagram Procedure A stack of three books, each weighing 5 lb, is sitting on top of a table. Draw the Free Body Diagram (FBD) of the top book.

11. Free Body Diagram Procedure 1. Sketch the isolated object. What is the isolated object? Top Book

12. Free Body Diagram Procedure 2. Sketch the applied and norm forces. When an object is in contact with and is supported by a second object, the second object can be replaced with a normal force which is perpendicular to the surface of the second object.

13. Free Body Diagram Procedure 2. Sketch the applied force and norm forces. Applied Force – Weight of top book Norm Force – Reaction force pushing up on the book, causing it not to fall

14. Free Body Diagram Procedure 3. Label objects and forces. W=5 lb. N=5 lb. PLTW – DE book

15. Free Body Diagram Practice F app FNFN WW FfFf θ θ Create a FBD for the children's sled pictured below. F app FfFf FNFN

16. Free Body Diagram Practice FNFN W W FNFN F app FfFf FfFf θ Create a FBD for the refrigerator pictured below.