Entry #5: Force

1. Entry #5: Force Watch : target accident http://www.youtube.com/watch?v=x_4TqtHATWI Answer: what happen? And why, share with your group and give the best answer to write on the board

2. Inertia • Watch the video http://www.youtube.com/watch?v=A6snX4M2_8U • and list at least 3 ideas about inertia

3. Check out yourself Washer and cup tryout • Put a piece of paper to cover the cup • Put one washer on the paper • Quickly remove the paper • What will happen to the washer? • Why

4. What factor(s) affect inertia? • http://www.youtube.com/watch?v=SIsl1TQEcCA&NR=1&feature=endscreen

5. Newton’s first law of motion: law of inertia • An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. • Objects tend to resist change http://teachertech.rice.edu/Participants/louviere/Newton/law1.html

6. Share with your group about your experience with inertia and choose one to share with the class

7. What do you need to do in the following situations (use arrow as force):

8. Feel the forces: types of forces

9. Forces • A force is a push or pull upon an object resulting from the object's interactionwith another object. • all forces (interactions) between objects can be placed into two broad categories: • contact forces • forces resulting from action-at-a-distance

10. Forces • Push/Pull: Fp - the force that one object pushes or pulls another object Use arrow to show force acting on the block What are the interaction objects for push and pull? which one give Fp? Which one receive Fp?

11. Forces • Friction: f • The force when 2 objects rub together • Pushes in the opposite direction of motion Use arrow to show friction force acting on the bear What are the interaction objects for friction? which one give f? Which one receive f?

12. Forces • Gravitational: Fg • Force of attraction between two objects • The force that pulls things toward Center of Earth Use arrow to show gravitational force acting on the ball What are the interaction objects for gravitational force? which one give Fg? Which one receive Fg?

13. Forces • Normal Force: Fn • Force pushing up on an object that is not moving and on a surface • Force is always perpendicular ( | ) to the line where the object and surface touch What are the interaction objects for normal force? which one give Fn? Which one receive Fn?

14. Forces • Tension: Ft • A pulling force of a string, wire, rubber band or something similar • Usually pulls up or away from the object Use arrow to show tension force acting on the block What are the interaction objects for tension force? which one give Ft? Which one receive Ft?

15. Forces • Electrostatic • Force between two charged objects • This force can pull two objects together or push them apart, depending on the charge of each object Use arrow to show electrostatic force acting on a hair What are the interaction objects for Fe? which one give Fe? Which one receive Fe?

16. Forces • Magnetic Force : Fm • A force that either pushes or pulls • Acts between two magnets, between a magnet and a magnetic object, or between an object with a magnetic field and a magnet or magnetic object Use arrow to show magnetic force acting on a clip What are the interaction objects for magnetic force? which one give Fm? Which one receive Fm?

17. Forces Contact Forces Frictional Force Tension Force Normal Force Air Resistance Force Applied Force (push and pull) elastic Force Action-at-a-Distance Forces Gravitational Force Electrical Force Magnetic Force

18. Describing Forces in Free Body Diagrams FNPE FNPE FGEP FGPE

19. How to draw a free body diagram: • Direction  • Amount/strength • Label: types of force: Fpush or pull , ffriction , FGravityFNormal, FTension , FElectrostatic, FMagnetic FP , f , FG , FN ,FT , FE , FM 4. Label: object acts On and By F OB 5. Object is represented by a dot

20. Force Diagram Warm-Up • identify the forces that the bowling ball has and by what object ( hint: force are interaction by two object, one give force and the other one receive force) • draw a picture to show all the forces the bowling ball received.

21. Force Label • FgAB By B object Type of Force On A object

22. Practice Force labels • Normal force on a ping-pong ball • Magnetic force on a paper clip • Electric force on balloon • Friction on block • Gravitational force on paper ball • Tension force on weights • Applied force on scales

23. Force Diagram • A dot represents an object • An arrow from the dot to show the force the object (dot) received • The length of the arrow represent the strength of the force • The arrow head represent the direction of the force • Label of Force: FgAB: gravitational force on object A by object B • Forces of different direction are originate from the object (the dot) • All the forces (arrows) will be balanced when the object does not move or move in constant velocity

24. Force Diagram Draw force diagram of the block Draw force diagram of the bear

25. Practice Force Diagrams • a ping-pong ball on water • a paper clip pulled by a magnet • Ball attracted to a wool • Block on Ramp • Weight hung by the rubber band

26. Exit ticket of force diagram • A book rests on a table • A book hangs from a spring