National 4/5 Physics

1. National 4/5 Physics • In addition to set homework you will be expected to • finish off class notes and regularly review work against • the learning outcomes. • You will be expected to take responsibility for your own • learning and for seeking help when you need it. At the • end of each section, you must ensure all notes are • completed and examples attempted.

2. In unit 1 we will learn about the physics of motion. We will focus on the language, principles and laws which describe and explain the motion of an object. Kinematics, also known as Mechanics is the science of describing the motion of objects using words, diagrams, numbers, graphs and equations. The goal is to develop mental models which describe and explain the motion of real-world objects.

3. Key words: vectors, scalars, distance, • displacement, speed, velocity. • By the end of this section you will be able to: • Describe what is meant by vector and scalar quantities • State the difference between distance and • displacement • State the difference between speed and velocity • State that force is a vector quantity • Use a scale diagram to find the magnitude and direction • of the resultant of two forces acting at right angles to • each other.

4. Key words: average speed • By the end of this section you will be able to: • Describe how to measure an average speed • Carry out calculations involving distance, time • and average speed.

5. Which of these are units of speed? metres • miles per hour gallons seconds minutes amperes miles kilometres per second miles per minute watts metres per second Newtons

6. Speeds in…. • In Physics we normally use units • m/s for velocity.

7. Average speed (m/s) Snail High speed train Sound 270 m/s 13.4 m/s 0.006 m/s UK town Fast jet 747 jumbo jet 29790 m/s 10.3 m/s 97 m/s Air molecule Earth in orbit Falcon 60 m/s 648 m/s 7500 m/s Olympic sprinter UK motorway Earth satellite 500 m/s 300000000 m/s 340 m/s Walking speed Light speed Concorde 1.7 m/s 31 m/s 833 m/s

8. Average speed ( m/s ) Light speed 300000000 m/s Earth in orbit 29790 m/s Earth satellite 7500 m/s Concorde 648 m/s Air molecule 500 m/s Fast jet 833 m/s Sound 340 m/s 747 jumbo jet 270 m/s Falcon 97 m/s High speed train 60 m/s UK motorway 31 m/s UK town 13.4 m/s Olympic sprinter 10.3 m/s Walking speed 1.7 m/s Snail 0.006 m/s

9. What is speed? • When we talk about speed we mean… • the distance covered by an object in a • given time.

10. What is speed? • If Hamish (the dog) runs 10 metres in 2 • seconds, what is his speed?

11. What is speed? • His speed is 5 metres per second. • So speed is

12. km Per Hour What is speed? • If you forget the formula think of cars travelling at 30 kilometres per hour =

13. Key words: average speed • By the end of this section you will be able to: • Describe how to measure an average speed • Carry out calculations involving distance, time • and average speed.

14. distance time speed

15. Speed Calculations • A cyclist travels 100 m in • 12 s. What is her speed?

16. Step 1: write down what you know. d = 100 m t = 12 s speed = ?

17. Step 2: write down your formula. You can use the triangle to help you but remember you get no marks for this! d = 100 m t = 12 s speed = ? d = speed x t

18. Step 3: substitute in your values. d = speed x t d = 100 m t = 12 s speed = ?

19. Step 4: rearrange d = speed x t 100 = speed x 12 d = 100 m t = 12 s speed = ?

20. Step 5: calculate d = speed x t 100 = speed x 12 speed = = 8.33 d = 100 m t = 12 s speed = ? 100 12

21. Step 6: units!!!! d = speed x t 100 = speed x 12 Speed = = 8.33 m/s d = 100 m t = 12 s speed = ? 100 12

22. Key words: average speed, instantaneous • speed • By the end of this section you will be able to: • Describe how to measure instantaneous speed. • Identify situations where average speed and • instantaneous speed are different.

23. Instantaneous and average speed • Are instantaneous and average speed the same?

24. Instantaneous or average? • A car’s speed between North Berwick and • Edinburgh • Average

25. Instantaneous or average? • The speed read from a car’s speedometer • Instantaneous

26. Instantaneous or average? • A tennis ball’s speed as it crosses the net • Instantaneous

27. Instantaneous or average? • A racing car’s speed over a lap of the track • Average

28. Instantaneous or average? • A parachutist’s speed as he/she lands • Instantaneous

29. Scalars and Vectors • Imagine a boat • making a distress • call to the • coastguard. • The boat tells the • coastguard he is 60 km • from Aberdeen.

30. Scalars and Vectors • Is this enough • information for the • coastguard to find • the boat?

31. Scalars and Vectors

32. Scalars and Vectors • The coastguard needs both • distance (size) • and • direction • to find the boat.

33. Scalars and Vectors - Definition • A scalar is a quantity which has only • magnitude (size). It is defined by a • number and a unit. • A vector is a quantity which has • magnitude (size) and direction. It is • defined by a number, a unit and a • direction.

34. Distance and Displacement A pupil walks from her house to her school. Her brother makes the same journey, but via a shop. How far has the girl walked? How far has her brother walked? 500 m 300 m 400 m

35. Distance and Displacement The girl has walked 500 m. Her brother has walked 700 m. Distance is a scalar quantity – it can be defined simply by a number and unit. 500 m 300 m 400 m

36. Distance and Displacement Distance is simply a measure of how much ground an object has covered. 500 m 300 m 400 m

37. 500 m 300 m 400 m Distance and Displacement But how far out of place is the girl? And her brother? Displacement is a vector which requires number, unit and direction.

38. Distance and Displacement The girl has a displacement of 500 m at a bearing of 117° East of North. 500 m 300 m 400 m

39. Distance and Displacement What is her brother’s displacement? 500 m 300 m 400 m

40. Distance and Displacement Her brother has a displacement of 500 m at a bearing of 117° (117° East of North). 500 m 300 m 400 m

41. Distance and Displacement Their displacement (how far out of place they each are) is the same. 500 m 300 m 400 m

42. Speed and Velocity Speed is a scalar quantity requiring only magnitude (number and unit). Velocity is a vector, requiring magnitude and direction.

43. Speed and Velocity Speed tells us how fast an object is moving. Velocity tells us the rate at which an object changes position.

44. Speed and Velocity • Imagine a person stepping one step • forward, then one step back at a speed of • 0.5 ms-1. • What is the person’s velocity? Remember • velocity keeps track of direction. The • direction of the velocity is the same as • the direction of displacement.

45. Speed and Velocity

46. Key words: vectors, scalars, distance, • displacement, speed, velocity. • By the end of this section you will be able to: • Describe what is meant by vector and scalar quantities • State the difference between distance and • displacement • State the difference between speed and velocity • State that force is a vector quantity • Use a scale diagram to find the magnitude and direction • of the resultant of two forces acting at right angles to • each other.

47. Distance and Displacement

48. Speed and Velocity

49. A physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North. The entire motion lasted for 24 seconds. Determine the average speed and the average velocity.

50. The physics teacher walked a distance of 12 meters in 24 seconds; thus, her average speed was 0.50 m/s. However, since her displacement is 0 meters, her average velocity is 0 m/s. Remember that the displacement refers to the change in position and the velocity is based upon this position change. In this case of the teacher's motion, there is a position change of 0 meters and thus an average velocity of 0 m/s.