Intermediate 2 Physics

1. Intermediate 2 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 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 lesson 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. Scalars and Vectors • Imagine a boat • making a distress • call to the • coastguard. • The boat tells the • coastguard he is 60 km • from Aberdeen.

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

6. Scalars and Vectors

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

8. 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.

9. Distance and Displacement How far has the girl walked? How far has her brother walked? A pupil walks from her house to her school. Her brother makes the same journey, but via a shop. 50 m 30 m 40 m

10. Distance and Displacement The girl has walked 50 m. Her brother has walked 70 m. Distance is a scalar quantity – it can be defined simply by a number and unit. 50 m 30 m 40 m

11. Distance and Displacement Distance is simply a measure of how much ground an object has covered. 50 m 30 m 40 m

12. 50 m 30 m 40 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.

13. Distance and Displacement The girl has a displacement of 50 m at a bearing of 117° East of North. 50 m 30 m 40 m

14. Distance and Displacement What is her brother’s displacement? 50 m 30 m 40 m

15. Distance and Displacement Her brother has a displacement of 50 m at a bearing of 117° (117° East of North). 50 m 30 m 40 m

16. Distance and Displacement Their displacement (how far out of place they each are) is the same. 50 m 30 m 40 m

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

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

19. 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.

20. Speed and Velocity

21. Key words: vectors, scalars, distance, • displacement, speed, velocity. • By the end of this lesson 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.

22. Distance and Displacement Virtual Int 2 Physics – Scalars and Vectors – Distance and Displacement

23. Speed and Velocity Virtual Int 2 Physics – Scalars and Vectors – Speed and Velocity

24. 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.

25. 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.

26. Scalar or Vector? Virtual Int 2 Physics – Scalars & Vectors - Introduction

27. Key words: vectors, scalars, resultant, scale diagram • By the end of this lesson 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.

28. Vectors • Vectors can be represented by a line • drawn in a particular direction. • The length of the line represents the • magnitude of the vector. • The direction of the line represents the • direction of the vector.

29. Addition of Vectors • When two or more scalars are added • together, the result is simply a numerical • sum. • For example a mass of 3kg and a mass of • 5 kg, when added, make a mass of 8kg.

30. Addition of Vectors • When two or more vectors are added • together, providing they act in the same • direction, the addition is straightforward. 5 N 3 N 8 N

31. Addition of Vectors • If they are acting in opposite directions 5 N 3 N 2 N

32. Addition of Vectors • The resultant of two or more vectors • which act at angle to each other can be • found either using a scale diagram, or by • Pythagoras and trigonometry. • Virtual Int 2 Physics – Scalars and Vectors -Adding Vectors

33. To find the resultant of a set of vectors using a scale diagram • 1. Decide on a suitable scale and write this • down at the start • 2 Take the direction to the top of the page as • North. Draw a small compass to show this. • 3 Draw the first vector ensuring it is the • correct length to represent the magnitude • of the vector, and it is the correct • direction.

34. To find the resultant of a set of vectors using a scale diagram • Draw an arrow to represent the second • vector starting at the head of the first. • Vectors are always added head to tail. • 5 The resultant vector can now be determined • by drawing it on the diagram from the tail • of the first to the head of the last vector. • The magnitude and direction of this vector • is the required answer. • 6 The final answer must have magnitude and direction – either a bearing from North or an angle marked clearly on the diagram

35. Scale Diagrams • Scale: remember if the question is in ms-1 then your scale should be a conversion from cm to ms-1. • Direction:draw compass on page • 1st vector:length and direction • 2nd vector: tail of 2nd starts at tip of first • Resultant vector:tail of 1st to tip of last • Answer must include magnitude (including units) and direction

36. Scale Diagrams • Direction should be given as a three • figure bearing from North • e.g. 045° or 175° or 035° • If you give any other angle, you must • clearly mark it on the scale diagram. Virtual Int 2 Physics – Scalars and Vectors -Adding Vectors 2 Virtual Int 2 Physics – Scalars and Vectors – Example Problem

37. A car travels 100 km South, then 140 km • East. The time taken for the whole • journey is 3 hours. • Using a scale diagram (and the six step • process) find • the car’s total distance travelled • its average speed • its overall displacement • its average velocity

38. Scale Diagrams • Scale diagrams are used to find the • magnitude and direction of the resultant • of a number of a set of vectors.

39. Key words: vectors, scalars, resultant, scale diagram • By the end of this lesson 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.

40. So you think you know your vectors and scalars? How do you write an answer which is a vector? Mass Distance Kinetic energy Scale diagram – 6 steps? Vector definition? Velocity= Velocity Force

41. Key words: vectors, resultant • By the end of this lesson you will be able • to: • Use Pythagoras and Trigonometry to find • the magnitude and direction of the • resultant of two forces acting at right • angles to each other.

42. The tropical island of Sohcahtoa

43. The tropical island of Sohcahtoa

44. The tropical island of Sohcahtoa

45. The tropical island of Sohcahtoa

46. hyp opp θ° adj

47. The Old Arab Carried A • Heavy Sack Of Hay • Tan = Opp/Adj; Cos= Adj/Hyp; • Sin=Opp/Hyp

48. hyp opp θ° adj

49. The squaw on the hippopotamus is equal • to the sum of the squaws on the other • two hides + =

50. N + 3 km North E 4 km East