1. What Are Forces ?

2. 1.What is a force? 2.How do we measure forces? 3.What are some common examples of forces Questions http://nnhsphysics670.pbworks.com/Intro-Forces-and- Free-Body-Diagrams

3. 1. What is a Force? Definition TermTerm SymbolUnitUnit Symbol

4. 1. What is a Force? Definition TermTerm SymbolUnitUnit Symbol force F newton N A force is a push or a pull.

5. What would you do to get a box to start moving?

6. Everyday language Physics language

7. What would you do to get a box to start moving? Everyday language Physics language To get the box to start moving I would PUSH the box.

8. What would you do to get a box to start moving?

9. Everyday language Physics language To get the box to start moving I would PUSH the box.

10. What would you do to get a box to start moving? Everyday language Physics language To get the box to start moving I would PUSH the box. To get the box to start moving I would APPLY a FORCE.

11. Consider Tug-of-War

12. Sarah’s team applies a ____________of 10 _______ to the ___________ on the rope. 10 N

13. Consider Tug-of-War Sarah’s team applies a___FORCE___of 10 NEWTONS to the ___LEFT________ on the rope. 10 N

14. Consider Tug-of-War Jaya’s team applies of ____________of 10 _______ to the ___________ on the rope.

15. Consider Tug-of-War Jaya’s team applies of ___FORCE___of 10 NEWTONS to the ___RIGHT________ on the rope. 10 N

16. Balanced Forces The __________ are ______________ in magnitude but ___________________ in direction. 10 N

17. Balanced Forces The FORCES are EQUAL in magnitude but OPPOSITE in direction. 10 N

18. Unbalanced Forces 20 N10 N

19. Unbalanced Forces 20 N10 N

20. Unbalanced Forces 20 N10 N

21. Net Force If two forces are acting in the same direction, they add together. …the impact of all forces acting on an object…

22. Net Force Example: Imagine Cindy is pulling a wagon to the right with a force of 5N, and Kelly is pushing the wagon to the right with a force of 7 N: 1. Draw an arrows to represent these forces on the wagon below. 2. What is the net force on the wagon? _____N + ____ N = _____ N 3. In what direction does the force act? _____________________ 4. The forces are _______________.

23. Net Force If two forces are acting in opposite directions, they subtract. …the impact of all forces acting on an object…

24. Net Force Example: Imagine Peter is pulling a treasure chest to the left with a force of 10 N, and Brian is pulling the treasure chest to the right with a force of 7 N. 1. Draw an arrows to represent these forces on the wagon below. 2. What is the net force on the wagon? _____N - ____ N = _____ N 3. In what direction does the force act? _____________________ 4. The forces are _______________.

25. Balanced Forces (net force = 0) Unbalanced Forces (net force ≠ 0) No change in motion Change in motion

26. Balanced vs. Unbalanced Forces Let’s look at two scenarios: 1.You are sitting on a chair. Do you think the forces on you are balanced? Why or why not?

27. Balanced vs. Unbalanced Forces continued… 2.A space shuttle is taking off. Do you think the force is balanced or unbalanced? Why or why not?

28. Question: How do unbalanced forces change motion? 1.______ things up 2.______ things down 3.Make things ______.

29. Practice with Net Force magnitude  how much? units  newtons direction  right, left, up, down

30. For you to Try: Worksheet--Practice with Net Force