Physics 4.1 “Changes in Motion”

I. ForceA. Intro…

1. What is force?2. What happens to objects when force is applied?3. What is the unit of force?

B. Action of Forces1. Contact Forces

a. Def – physical contact between two objectsb. Ex: catching a basketball

2. Field Forcesa. Def – No physical contact between objectsb. Ex: Magnetic field’s effect on a compass

3. Balloon and water Demoa. Is this a field or contact force?

II. Force Diagrams

A. Force is a vector1. use arrows to represent forces2. Force Diagram

a. All forces are drawn that act on an objectb. Tail is attached to object

B. Free Body Diagram – shows only forces acting on the object of interest

1. How to draw a free body diagram…a. Draw the isolated object

-position the object accordinglyb. Draw and label vector arrowsc. Only draw forces that act on the objectd. Used to find the net force that acts on the

object

C. Hot Wheel Exercise1. 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.

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