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# Force & Motion

intro to force & motion 9th grade level

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### Force & Motion

1. 1. Motion & Forces
2. 2. Speed & Velocity <ul><li>Speed - the rate of change in position over time (distance/time) </li></ul><ul><li>Instantaneous speed </li></ul><ul><li>Average speed </li></ul><ul><li>How is velocity different from speed? </li></ul>Velocity describes both speed and direction
3. 3. Change in Velocity <ul><li>What makes an object change velocity? </li></ul>
4. 4. Force <ul><li>Push or Pull </li></ul><ul><li>Forces can cause a change in velocity </li></ul><ul><li>Examples: </li></ul>Gravity Magnetism Friction
5. 5. Balanced Forces <ul><li>Forces that </li></ul><ul><ul><li>act on the same object </li></ul></ul><ul><ul><li>are opposite in direction </li></ul></ul><ul><ul><li>are equal in size </li></ul></ul>
6. 6. Balanced Forces <ul><li>Book on table </li></ul><ul><ul><li>Weight of the book is downward force caused by gravity </li></ul></ul><ul><ul><li>Table pushes back with an equal and opposite force </li></ul></ul><ul><li>Net force is zero </li></ul>
7. 7. Unbalanced Forces <ul><li>Forces that are NOT opposite and equal </li></ul><ul><li>What do they cause? </li></ul><ul><li>CHANGE IN VELOCITY </li></ul><ul><li>ACCELERATION </li></ul>
8. 8. Friction <ul><li>Force that opposes motion between 2 surfaces </li></ul><ul><li>Depends on the: </li></ul><ul><ul><ul><li>types of surfaces </li></ul></ul></ul><ul><ul><ul><li>force between the surfaces </li></ul></ul></ul>
9. 9. Types of Friction <ul><li>Static Friction: (Couch Potato) </li></ul><ul><ul><li>Force between objects at rest </li></ul></ul><ul><li>Sliding Friction: (Ice skating) </li></ul><ul><ul><li>Solid surfaces slide over each other </li></ul></ul><ul><li>Rolling Friction: (Rollerblading) </li></ul><ul><ul><li>An object rolls over a surface . </li></ul></ul><ul><li>Fluid friction: (Submarine) </li></ul><ul><ul><li>An object moves through a fluid </li></ul></ul>
10. 10. Friction <ul><li>Friction is greater... </li></ul><ul><ul><li>between rough surfaces </li></ul></ul><ul><ul><li>when there’s greater force between surfaces (such as more weight) </li></ul></ul>
11. 11. Lubricant <ul><li>Changes sliding friction into fluid friction </li></ul>
12. 12. Friction <ul><li>Is friction always bad? </li></ul>
13. 13. Gravity <ul><li>The attractive force between all objects in the universe </li></ul>
14. 14. Acceleration of Gravity <ul><li>Near the surface of the earth the acceleration due to gravity is 9.8 m/s/s </li></ul>
15. 15. Newton’s 1 st Law <ul><li>An object at rest remains at rest and an object in motion will continue moving at a constant velocity unless acted on by unbalanced forces. </li></ul>
16. 16. Newton’s Laws of Motion
17. 17. Newton’s 1 st Law <ul><li>INERTIA </li></ul><ul><li>tendency of an object to resist any change in its motion </li></ul><ul><li>increases as mass increases </li></ul>
18. 18. Newton‘s 2 nd Law <ul><li>If more force is applied, an object will be accelerated _____ </li></ul>more
19. 19. Newton’s 2 nd Law <ul><li>More force means more acceleration </li></ul><ul><li>More mass means less acceleration </li></ul><ul><li>Force = mass X acceleration </li></ul>F = ma
20. 20. Newton’s 3 rd Law <ul><li>For every action, there is an equal and opposite reaction. </li></ul><ul><li>Forces occur only in pairs </li></ul><ul><ul><li>Act on different objects </li></ul></ul><ul><ul><li>Equal and opposite </li></ul></ul>
21. 21. Newton’s 3 rd Law <ul><li>The hammer exerts a force on the nail to the right. </li></ul><ul><li>The nail exerts an equal but opposite force on the hammer to the left. </li></ul>
22. 22. Momentum
23. 23. Terminal Velocity <ul><li>The final speed of a falling object. </li></ul>
24. 24. Terminal Velocity <ul><li>Air resistance is offsetting the the weight of the object </li></ul>
25. 26. Forces End
26. 27. Force <ul><li>Aristotle's idea: </li></ul><ul><li>For an object to move at a constant speed, a constant force must be applied. </li></ul>
27. 28. Force <ul><li>Newton’s idea: </li></ul><ul><li>An object moving at a constant speed will continue at that speed without additional force being applied. </li></ul>
28. 29. Balanced Forces