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

2. Today’s Learning Objective Review   Identify types of forces. New   Identify and describe balanced and unbalanced forces.

3. Think, pair and share… 1. 1.Draw the diagram below in your journal. 2. 2.What would happen if both people pushed in the same direction? Why? 3. 3.What happens when the people are pushing in the opposite direction? Why? 4. 4.Write your answers in your journal and then share with your partner.

4. Group Problem-Solving Task   How can you determine which of these two boxes will feel heavier when lifted? Rules: You may not lift either of the boxes. You may not look inside either of the boxes. Task: 1. 1.Discuss with your group what the problem and the rules mean to you. 2. 2.Develop a plan for solving the problem. 3. 3.As a group write your own definition for force.

5. Force Force  a push or pull that one object exerts on another  A force has both size and direction F kick F gravity

6. What are some common forces?  Gravitational Force (Gravity)  Friction  Applied force  Balanced Force  Unbalanced Force

7. How do we measure Force?   We use a Spring Scale to measure force.   The unit of measurement for force is Newtons.

8. Let’s Review! 1. 1.What is Mass? 2. 2.What tool do we use to measure Mass? What is the unit of measurement? 3. 3.What is Weight? 4. 4.What tool do we use to measure Weight? What is the unit of measurement?

9. Let’s Review! 1. What is Mass? The amount of matter in an object 2. What tool do we use to measure Mass? Triple Beam Balance What is the unit of measurement? Grams 3. What is Weight? Weight Is a measure of gravitational force on an object. 4. What tool do we use to measure Weight? Spring Scale What is the unit of measurement? Newtons

10. What are some common forces? Gravitational Force (Gravity)– The force of attraction between objects that is due to their masses. Weight- is a measure of gravitational force on an object.  We measure weight (force) with a Spring Scale.  Unit = Newtons

11. What are some common forces? Friction – a force that opposes motion at a contact between two surfaces. Air resistance is a type of friction.

12. What are some common forces? Applied force – a force applied to an object by a person or another object.

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

14. Balanced Forces  forces acting on an object that are opposite in direction and equal in size  no change in position, direction of motion or speed of an object

15. Unbalanced forces  Opposing forces that are not equal  Causes change in position, direction of motion and speed of an object F friction W F pull F net NN

16. 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?

17. Balanced and unbalanced Forces Module http://www.engineeringinteract.org/resourc es/parkworldplot/flash/concepts/balanced andun.htm http://www.engineeringinteract.org/resourc es/parkworldplot/flash/concepts/balanced andun.htm