1. Physics 4.1 “Changes in Motion”

2. I. Force A. Intro… 1. What is force? 2. What happens to objects when force is applied? 3. What is the unit of force? B. Action of Forces 1. Contact Forces a. Def – physical contact between two objects b. Ex: catching a basketball 2. Field Forces a. Def – No physical contact between objects b. Ex: Magnetic field’s effect on a compass 3. Balloon and water Demo a. Is this a field or contact force?

3. II. Force Diagrams A. Force is a vector 1. use arrows to represent forces 2. Force Diagram a. All forces are drawn that act on an object b. Tail is attached to object B. Free Body Diagram – shows only forces acting on the object of interest

4. 1. How to draw a free body diagram… a. Draw the isolated object -position the object accordingly b. Draw and label vector arrows c. Only draw forces that act on the object d. Used to find the net force that acts on the object

5. C. Hot Wheel Exercise 1. Draw a force diagram for a car that is sitting on the table. 2. Draw a force diagram for a car that is in motion on the table. 3. Draw a force diagram for a car that has run into a book. 4. Draw a free body diagram for a car that has run into a book. #1 #2 #3 #4