Physics:

1. Physics: Motion and Energy, Forces, Forces and Fluids

2. Notes 9-1 & 9-2 Motion and Speed

3. Motion • An object is in motion if it changes position relative to a reference point • Stationary objects make good reference points

4. Relative Motion • Whether or not an object is in motion depends on the reference point you choose.

5. Distance and Displacement • Distance is the total length of the actual path between two points. Displacement is the length and direction of a straight line between starting and ending points. What is the total distance this person traveled (in blocks)? 7 Blocks What is the total displacement of this person? 5 Blocks Northeast

6. Vectors • Quantities that have both a magnitude and a direction • Example: Displacement

7. Calculating Speed • If you know the distance an object travels in a certain amount of time, you can calculate the speed of the object.

9. Average Speed • The speed of most moving objects is not constant

10. Instantaneous Speed • Rate at which object is moving at a given instant in time

11. Velocity • Speed in a given direction • Velocity is a vector because it has both magnitude and direction • Changes in velocity may be due to changes is speed, changes in direction, or both

12. Graphing Motion • You can use distance-versus-time graphs to interpret motion.

13. Let’s Review!

14. Review Questions 1. Is a moving bus a good reference point from which to measure your position? a. No, because it is often late. b. No, because it is not a stationary object. c. Yes, because it is very large. d. Yes, because it can travel very far.

15. Review Questions 1. Is a moving bus a good reference point from which to measure your position? a. No, because it is often late. b. No, because it is not a stationary object. c. Yes, because it is very large. d. Yes, because it can travel very far.

16. Review Questions 2. To describe a friend’s position with respect to you, you need to know a. Your friend’s distance from you. b. The direction your friend is facing. c. Your friend’s distance and direction from you. d. Your friend’s distance from a nearby object.

17. Review Questions 2. To describe a friend’s position with respect to you, you need to know a. Your friend’s distance from you. b. The direction your friend is facing. c. Your friend’s distance and direction from you. d. Your friend’s distance from a nearby object.

18. Review Questions 3. Two cars traveling in the same direction pass you at exactly the same time. The car that is going faster a. moves farther in the same amount of time. b. has more mass. c. has the louder engine. d. has less momentum.

19. Review Questions 3. Two cars traveling in the same direction pass you at exactly the same time. The car that is going faster a. moves farther in the same amount of time. b. has more mass. c. has the louder engine. d. has less momentum.

20. Review Questions 4. To describe an object’s motion, you need to know its a. position. b. change in position. c. distance. d. change in position over time.

21. Review Questions 4. To describe an object’s motion, you need to know its a. position. b. change in position. c. distance. d. change in position over time.

22. Notes 9-3 Acceleration

23. Acceleration • Rate velocity changes with time • Vector quantity • In science, acceleration refers to increasing speed, decreasing speed, or changing direction • Decreasing speed = deceleration

24. Chapter 9 Motion and Energy Calculating Acceleration • To determine the acceleration of an object, you must calculate its change in velocity per unit of time. • Acceleration = Final Velocity – Initial Velocity Time

25. Let’s Try a Problem • Calculate the plane’s acceleration in the first 5 seconds of motion. A= Vf – Vi time A = 40 m/s – 0 m/s 5 s A = 8 m/s2

26. As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Read and Understand What information have you been given? Initial velocity = 4 m/s Final velocity = 22 m/s Time = 3 s Chapter 9 Motion and Energy Calculating Acceleration

27. As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Plan and Solve What quantity are you trying to calculate? The acceleration of the roller-coaster car = __ What formula contains the given quantities and the unknown quantity? Acceleration = (Final velocity - Initial velocity)/Time Perform the calculation. Acceleration = (22 m/s - 4 m/s)/3 s = 18 m/s/3s Acceleration = 6 m/s2 The acceleration is 6 m/s2 down the slope . Chapter 9 Motion and Energy Calculating Acceleration

28. As a roller-coaster car starts down a slope, its velocity is 4 m/s. But 3 seconds later, its velocity is 22 m/s in the same direction. What is its acceleration? Look Back and Check Does your answer make sense? The answer is reasonable. If the car’s velocity increases by 6 m/s each second, its velocity will be 10 m/s after 1 second, 16 m/s after 2 seconds, and 22 m/s after 3 seconds. Chapter 9 Motion and Energy Calculating Acceleration

29. Practice Problem A falling raindrop accelerates from 10 m/s to 30 m/s in 2 seconds. What is the raindrop’s acceleration? (30 m/s - 10 m/s) ÷ 2 seconds = 10 m/s2 Chapter 9 Motion and Energy Calculating Acceleration

30. Practice Problem A certain car can accelerate from rest to 27 m/s in 9 seconds. Find the car’s acceleration. (27 m/s - 0 m/s) ÷ 9 s = 27 m/s ÷ 9 s = 3 m/s2 Chapter 9 Motion and Energy Calculating Acceleration

31. Chapter 9 Motion and Energy Graphing Acceleration • You can use both a speed-versus-time graph and a distance-versus-time graph to analyze the motion of an accelerating object.

32. Mr. Edmonds!! • http://youtu.be/4CWlNoNpXCc

33. Bonus: Newton’s Laws • 1st Law: An object will remain at rest or moving at a constant velocity unless it is acted upon by an unbalanced force. • 2nd Law: Acceleration depends on the net force acting on the object and on the object’s mass. • 3rd Law: If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.

34. 10-1 Notes Forces

35. What is a force? • A push or pull • Vector quantity • Described by its magnitude and by the direction in which it acts • Arrow represents direction • Magnitude unit = Newton (N)

36. Net Force • Often there is more than one force acting on an object at the same time • The result is net force, a combination of all the forces • Net force determines whether an object moves and in which direction

37. Combining Force Vectors • The strength and direction of the individual forces determine the net force.

38. Unbalanced Forces • Unbalanced forces acting on an object result in a net force and cause a change in the object’s velocity.

39. Balanced Forces • Balanced forces acting on an object do not change the object’s velocity.

40. Newton’s First Law of Motion • An object will remain at rest or moving at a constant velocity unless it is acted upon by an unbalanced force • Inertia is the tendency of an object to resist a change in motion • Newton’s First Law of Motion = The Law of Inertia

41. Notes 10-2 (Part I) Friction & Gravity

42. Friction • A force 2 surfaces exert on each other when they rub against each other • Acts as an unbalanced force to slow motion down • The strength of the force of friction depends on the types of surfaces involved and how hard the surfaces push together • 4 types of friction

43. 1) Static Friction • Acts on objects that are not moving • You must exert a force greater than the force of static friction to make the object move

44. 2) Sliding Friction • Occurs when two solid surfaces slide over each other

45. 3) Rolling Friction • Occurs when an object rolls across a surface • Rolling friction is less than sliding friction for similar surfaces

46. 4) Fluid Friction • Occurs when a solid object moves through a fluid, such as air, water, oil, etc. • Fluid friction is usually less than sliding friction

47. Gravity • Force that pulls towards the center of the earth • Newton realized that gravity acts everywhere, not just on earth • Called the Law of Universal Gravitation • Any 2 objects in the universe attract each other

48. Gravity Between Objects • The force of gravity between objects increases with greater mass and decreases with greater distance.

49. Mass and Weight • Mass is how much matter is in an object • The gravitational force exerted on a person or object at the surface of a planet is known as weight. • Weight = Mass x Acceleration due to gravity Acceleration due to gravity at Earth’s surface = 9.8 m/s2

50. Free Fall • If the only force acting on the object is gravity, it is said to be in free fall • An object in free fall is accelerating because of the force of gravity at a rate of 9.8 m/s/s • This means that every second an object is free falling, it increases its velocity 9.8 m/s • Is this affected by mass? If dropped from the same height at the same time, will a heavier object fall faster?