1. Forces You will be able to: ● Identify and describe the changes in position, direction, and speed of an object when acted upon by unbalanced forces. ● Identify balanced and unbalanced forces. Adapted from a PowerPoint by Kathleen Ingram, Lamar Middle School

2. What are some common forces? Gravity – the force with which the earth, moon, or another massive object attracts another object towards itself.

3. What are some common forces? Normal force – a support force exerted upon an object in contact to another object.

4. Net Force The net force is the combined effect of all forces acting on an object.

5. Force Balanced Forces  forces acting on an object that are opposite in direction and equal in size  no change in speed

6. Force Unbalanced forces  unbalanced forces that are not opposite and equal  velocity changes (object accelerates) F friction W F pull F net NN

7. Are there different forces acting on the figure skaters? What direction are the forces acting? Are the forces balanced or unbalanced? How do you know?

8. Balanced and unbalanced forces http://www.engineeringinteract.org/resourc es/parkworldplot/flash/concepts/balanced andun.htm http://www.engineeringinteract.org/resourc es/parkworldplot/flash/concepts/balanced andun.htm

9. Today we will demonstrate… (A)basic relationships between force and motion using simple machines including pulleys and levers (A)that an object will remain at rest or move at a constant speed and in a straight line if it is not being subjected to an unbalanced force (B)how unbalanced forces cause changes in the speed or direction of an object's motion

10. Tug of War  drawing

11. Force Problems 20 N What is the net force? Are the forces balanced or unbalanced? Describe the motion of the object. (none, accelerate to left, accelerate to right) 20 N

12. Force Problems 20 N What is the net force? Are the forces balanced or unbalanced? Describe the motion of the object. (none, accelerate to left, accelerate to right) 30 N

13. Force Problems 20 N What is the net force? Are the forces balanced or unbalanced? Describe the motion of the object. (none, accelerate to left, accelerate to right) 10 N

14. Force Problems 20 N What is the net force? Are the forces balanced or unbalanced? Describe the motion of the object. (none, accelerate to left, accelerate to right) 30 N

15. Force Problems 30 N What is the net force? Are the forces balanced or unbalanced? Describe the motion of the object. (none, accelerate to left, accelerate to right) 30 N