2. I wonder if other dogs think poodles are members of a weird religious cult. - Rita Rudner

3. Chapter Menu Lesson 1:Combining ForcesCombining Forces Lesson 2:Types of ForceTypes of Force Lesson 3:Unbalanced Forces and AccelerationUnbalanced Forces and Acceleration Click on a hyperlink to view the corresponding lesson.

4. force net force unbalanced forces balanced forces Newton’s first law of motion 2.1 Combining Forces

5. Force 2.1 Combining Forces A push or a pull on an object is a force. I wonder if other dogs think poodles are members of a weird religious cult. - Rita Rudner

6. Force A. Force is a Vector B. Force has a direction and a magnitude. C. Force is measured in Newtons. 2.1 Combining Forces

7. Combining Forces A. The force on an object is the combination of all forces on that object B. The resulting force of all the forces is called net force. 2.1 Combining Forces

8. Forces in the Same Direction A.When forces in the same direction combine, 1. the net force is in the same direction 2. the size of the net force are the forces added together. 2.1 Combining Forces

9. Combining Forces in the Same Direction (cont.) If two people push the dresser to the right, the forces are added together. 2.1 Combining Forces

10. Forces in Opposite Directions A.Combining forces in opposite direction= 1. the net force is in the direction of the larger force. 2. The size of the net force is the difference between the two forces. 2.1 Combining Forces

11. Combining Forces in Opposite Directions (cont.) Two people exerting a force in opposite directions show how vectors combine to create net force. 2.1 Combining Forces

12. Unbalanced and Balanced Forces A. If the net force on an object is not zero, it is an unbalanced force. B. If the net force on an object equals zero, it is a balanced force. 2.1 Combining Forces ONLY UNBALANCED FORCES CAUSE CHANGE IN MOTION!

13. Balanced Forces 2.1 Combining Forces

14. Balanced Forces and Motion If two people push with the same force, the door does not move. 2.1 Combining Forces The forces have the same magnitude. The forces are in opposite directions. The net force on the door is zero and the forces are balanced. The motion of the door does not change.

15. Unbalanced Forces and Motion Unbalanced forces change motion. If two people push with different force, the door moves. The forces have a different magnitude and are in opposite directions. The net force on the door is not zero and the forces are unbalanced. The door moves in the direction of the larger force. 2.1 Combining Forces

16. Lesson 1 Review Which of the following changes occur when an unbalanced force acts on an object? Amotion Bmass Cinertia Dweight 2.1 Combining Forces

17. Lesson 1 Review What is the net force acting on a door if one person pushes to the right with a force of 2000 N and a second person pushes with a force of 1500 N to the right? A3500 N to the right B3500 N to the left C500 N to the left D500 N to the right 2.1 Combining Forces

18. Lesson 1 Review You are riding a bike. In which of the following situations are the forces acting on the bike balanced? AYou pedal to speed up. BYou turn at constant speed. CYou coast to slow down. DYou pedal at constant speed. 2.1 Combining Forces

19. End of Lesson 1

20. gravity law of universal gravitation weight friction elastic force tension force 2.2 Types of Forces compression force normal force

21. Which is fundamental force we all know? 1.Gravity is an attractive force between all objects that have mass in the entire UNIVERSE, 2.Also known as Law of Universal Gravitation Predict the forces acting on the object? 2.2 Types of Forces

22. Gravity (cont.) The ball does not travel in a straight line because of the unbalanced force of gravity acting on it. 2.2 Types of Forces

23. 2. Gravity rules 1.Gravity is stronger when objects are closer 2. Weaker when farther apart 3.The more mass, the more gravity 4.Smaller mass, less gravity 5.F= Gm 1 m 2 /r 2 (G=6.673x10 -11 ) 2.2 Types of Forces

24. The Law of Universal Gravitation (cont.) The gravitational force becomes stronger as either or both objects increase in mass. The gravitational force becomes weaker as the distance between the objects increases. 2.2 Types of Forces

25. 3. What’s does gravity have to do with Weight and Mass? NOTE: Mass is the amount of matter in an object and does not change with location. A. Weight is the gravitational force on a object and changes with location. 2.2 Types of Forces Where would you weigh less?

26. Question Time 1. Give an example of something that has gravity. 2. What are the two ways to increase the size of the force of gravity? 3. What changes as you get farther from the Earth, mass or weight? 4. What is the formula for speed?

27. B. Friction 1. Friction is a force that opposes motion Matter isn’t smooth, so things get caught on each other 2.2 Types of Forces Friction increase as motion/force increases! Friction increases with rougher surfaces! Lubricants reduce friction Surface area doesn’t matter! (except fluids)

28. Friction i. Usually friction is present and an unbalancing force must be applied to keep an object moving. ii. When there is very little friction, objects move with near constant velocity, with NO other forces required

29. 2. Static Friction A. Static friction is the force between two surfaces in contact that keeps them from sliding when a force is applied. 2.2 Types of Forces If the object doesn’t move as you push on it with more and more force Then the forces are balanced Which means that static friction increases to match your force on the book Keeps things in place! Always a Balanced forces

30. 2. Sliding Friction 2.2 Types of Forces The frictional force that acts on the sliding object is called sliding friction. (duh)

31. Sliding Friction (cont.) The book pushed across the table slows down because of sliding friction. Without sliding friction, the book would continue moving without a force being applied. 2.2 Types of Forces

32. Friction 2.2 Types of Forces Other types of Friction: 3. Rolling Friction 4. Fluid Friction (air and water resistance)

33. Question time i. Friction is a force that ______ motion ii. What kind of friction keeps a car from moving when you push on it? iii. What is one way to increase friction? iv. What are the four types of friction?

34. C. Elastic Forces 1. An elastic force occurs when a material is stretched or compressed. 2.2 Types of Forces 3 Types of Elastic Force 1. Tension 2. Compression 3. Normal

35. 2. Tension A tension force is a pulling force exerted by an object when it is stretched, such as a rubber band. 2.2 Types of Forces

36. 3. Compression A compression force is a pushing force exerted by a material when it is squeezed or compressed. Compression force always balances the force pushing on it 2.2 Types of Forces

37. 4. Normal Forces A normal force is the force exerted by an object that is perpendicular to the surface of the object. 2.2 Types of Forces

38. Normal Forces (cont.) The cup is exerting a downward force on the table, caused by gravity. The table is exerting an upward normal force on the cup, caused by compression. 2.2 Types of Forces

39. Question time I. What kind of force does a rubber band exert when you stretch it? II. Give an example of a compression force? III. What are elastic forces? IV. What is the “normal” force? V. Why is tension important to a bridge? VI. Why is compression important to a bridge?

40. Forces in the Horizontal Direction Friction balances forces applied in a horizontal direction, usually Friction equals the horizontal force on an object that is not changing motion. 2.2 Types of Forces

41. Forces in the Vertical Direction Upward normal force balances the downward force of gravity on an object that is not moving vertically. 2.2 Types of Forces

42. Forces in the Vertical Direction (cont.) 2.2 Types of Forces

43. Lesson 2 Review A(n) ____ force is the force exerted by an object that is perpendicular to the surface of the object. Acompression Belastic Cnormal Dtension 2.2 Types of Forces

44. Lesson 2 Review Which force causes a rolling ball to slow down? Asliding friction Bstatic friction Cnormal force Dgravity 2.2 Types of Forces

45. Lesson 2 Review The gravitational force between two objects ____ as ____ increases. Aincreases; distance Bdecreases; mass Cincreases; velocity Ddecreases; distance 2.2 Types of Forces

46. End of Lesson 2

47. Chapter Assessment California Standards Practice Concepts in Motion Image Bank Science Online Chapter Resources Menu Click on a hyperlink to view the corresponding feature.

48. If a student pushes a book across a table with a force of 10 N and the force of friction is 2 N, what is the net force on the book? A0 N B2 N C8 N D12 N Chapter Assessment 1

49. What would cause an object to have a larger acceleration? Aincreasing the net force applied Bdecreasing the net force applied Cincreasing the mass and keeping the net force constant Dnone of the above Chapter Assessment 2

50. What causes a change in motion on an object? Azero net force Bunbalanced force Cweight Dbalanced force Chapter Assessment 3

51. A car is driving at a constant velocity. Which of the following statements is true? AA balanced force keeps it moving. BThe car is moving in a circle. CAn unbalanced force keeps it moving. DFriction keeps the car moving. Chapter Assessment 4

52. For every action force, there is a reaction force that is ____. Ain the same direction Bequal to the two objects Cequal and in the opposite direction Dunequal and in the direction of the object with less mass Chapter Assessment 5

53. Which of the following best describes why force is a vector? Aspeed and size Bmagnitude Cdirection and friction Dmagnitude and direction CA Standards Practice 1 SCI 2.a

54. Two people are pushing in opposite directions on a box. One person is pushing to the left with a force of 250 N, the other is pushing to the right with a force of 400 N. What is the resulting force vector? A150 N to the right B650 N to the right C150 N to the left D400 N to the right CA Standards Practice 2 SCI 2.b

55. You throw a 0.9 kg ball with a force of 17 N. What is the ball’s acceleration? A0.05 N B15.3 N C13.3 m/s 2 D18.9 m/s 2 CA Standards Practice 3 SCI 2.e, 2.f

56. A tennis ball hit by a racket has an acceleration of 2000 m/s 2. If the net force on the tennis ball is 125 N, what is the tennis ball’s mass? A16 kg B0.25 kg C0.06 kg D0.43 kg CA Standards Practice 4 SCI 2.f

57. What balanced forces are acting on a book sliding across a table? Agravity Bgravity and friction Csliding friction, normal force, and gravity Dgravity and normal force CA Standards Practice 5 SCI 2.d

58. Concepts in Motion 1

59. Image Bank

60. End of Resources