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GCSE Physics double award notes

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• What other quantities must be accompanied by a direction as well as its size?
• What physical quantities do we need to be able to work out the acceleration of something? Mark Cavendish – video clip of tour de France, final stage (21, coming into Paris at the Arc de Triomphe). During the last 200 m Cav is known as a legend for accelerating up to 48 mph to snatch a win (world record for someone from the UK, winning 6 stages at only 24 years-old)
• Michael Johnston left speechless! http://news.bbc.co.uk/sport1/hi/athletics/8204766.stm First 30 m, t = 3.78 s, u = 0 m/s, v = 11.11 m/s, a = 2.94 m/s^2 Last 20 m, t = 9.58 - 7.92 = 1.66 s , u = 12.20 m/s, v = 12.05 m/s, a = -0.09 m/s^2
• Shallow slope up Steep slope up Slope down Negative Positive low Positive high Continually changing Steep to shallow Shallow to steep
• Wind-up racer’s motion
• Red Bull Stratos – Felix Baungartner and Joe Kittinger As this piece of historic motion is yet to be done we unfortunately don’t have any speeds to work with but we were luck enough to catch up with Felix on a stretch of road through the country side where he allowed us to film. So here we go, pens at the ready, take down the distance at 5 second intervals and then we’ll replay the high-octane action for speed.
• Video clip of v-t, results table time 0 – 30, take results every second (vertically down) Time axis – every box 2 seconds Velocity axis – every box 5 m/s
• Talk through the ‘journey’ Label acceleration, deceleration, speeding up, slowing down, steady speed, zero speed and low &amp; high speed Calculate acceleration during 1 st five seconds – 12 m/s^2 From 5 s to 8 s (6-60)/3 = -18 m/s^2
• Which is more impressive, Neo dealing with being shot at or Hancock saving someone’s life? How could we judge who is the most awesome? Vid clips, Neo with the bullet-stopping and Hancock with the train-stopping What did Neo do at the start of the clip and what physical factor was it that he so impressively controlled? Extremely fast speed (or velocity). Hancock did something similar but it was a different physical factor that made his ability so impressive, what was it? Both superheroes are controlling the ‘momentum’ of the objects, and in these examples each object has a great deal of momentum! In Science momentum is ‘ mass in motion ’ Momentum of a football team, they’re hard to stop – they’ve built up a lot of pace
• ### Motion

1. 1. Motion GCSE Physics
2. 2. Book Reference <ul><li>Page 66 </li></ul>
3. 3. Learning Intentions <ul><li>By the end of the lesson we will be able to… </li></ul><ul><li>State the difference between displacement and distance </li></ul><ul><li>Recall the equation for calculating speed and apply it to solve simple problems </li></ul><ul><li>State the difference between speed and velocity </li></ul>
4. 4. By definition… <ul><li>Distance (…travelled)- the total length of journey taken from start to finish (metre) </li></ul><ul><li>Displacement - a measure of the overall change of position, including the direction (metre with direction) </li></ul>Eg. Distance travelled is 8 metres Displacement is 4 metres, east 2m 2m 4m N Start Finish
5. 5. Questions <ul><li>A man drives from Ballymena to Coleraine. The 2 towns are 22 miles apart. </li></ul><ul><li>What is the distance travelled? </li></ul><ul><li>What is his displacement? </li></ul><ul><li>What is his displacement if he turns around at Coleraine and stops at Ballymoney? </li></ul><ul><li>a) 22 miles b) 22 miles N c) 14 miles N </li></ul>Ballymena Coleraine Ballymoney 8 miles
6. 6. Displacement <ul><li>Extra wee bit </li></ul><ul><li>The displacement of an object after a journey can be zero- </li></ul><ul><li>The total distance travelled was 50 metres </li></ul>25m A B Journey A – B and then B - A A B Total displacement from A to B and B back to A… zero 10m
7. 7. Speed The rate at which an object changes the distance it has travelled is called its speed . For a complete journey the speed of an object can be calculated by dividing the total distance covered by the time taken to complete the journey- Average Speed = Total Distance / Time Taken metres/second = metre / second Ferrari 360 Spider speed distance time
8. 8. <ul><li>This is the quantity given to the displacement travelled in unit time in a given direction </li></ul><ul><li>OR </li></ul><ul><li>The rate of change of displacement </li></ul><ul><li>Velocity is a vector quantity </li></ul><ul><li>e.g. the bike’s velocity is 24 m/s East </li></ul>Size direction Lance Armstrong
9. 9. Scalar versus Vector <ul><li>Scalars are quantities which are only described by their size </li></ul><ul><li>Vectors are quantities which require both a size and a direction. </li></ul>
10. 10. Question Time <ul><li>Page 69 </li></ul><ul><li>Questions 1-4 </li></ul>1 mile = 1600 m
11. 11. Learning Intentions <ul><li>By the end of the lesson we will be able to… </li></ul><ul><li>Recall the equation for calculating acceleration and apply it to solve simple problems </li></ul><ul><li>Recognise acceleration as a vector quantity </li></ul>
12. 12. <ul><li>Which object has the greatest Acceleration? </li></ul>
13. 13. Snap Shots <ul><li>Constant Velocity </li></ul><ul><li>Changing Velocity </li></ul>Disp Disp.
14. 14. <ul><li>The average acceleration of an object is given by the change in velocity per unit time- </li></ul>Acceleration = Change in Velocity / Time Taken Acceleration = ( Final Velocity – Initial Velocity ) / Time Taken a = (v – u) / t m/s 2 = m/s / s a t Δ v
15. 16. Usain Bolt’s Acceleration <ul><li>Work out Usain’s change in motion during </li></ul><ul><ul><li>first 30 metres </li></ul></ul><ul><ul><li>last 20 metres </li></ul></ul>
16. 17. Wee bit extra <ul><li>Acceleration is a vector quantity. It can be a positive or negative value. </li></ul><ul><li>When an object’s initial velocity is greater than the final velocity then it is said to be slowing down or decelerating (negative acceleration) </li></ul>
17. 18. Examples <ul><li>Example A </li></ul><ul><li>Acceleration = change in velocity / time taken </li></ul><ul><li>= (8 – 0) / 4 </li></ul><ul><li>= 8 / 4 = 2 m/s 2 </li></ul><ul><li>Example B </li></ul><ul><li>a = Δ v / t </li></ul><ul><li>= (0 – (-8)) / 4 </li></ul><ul><li>= 8 / 4 = 2 m/s 2 </li></ul>
18. 19. Complete the Chart showing steady acceleration <ul><li>All Velocities are in m/s </li></ul><ul><li>Calculate the accelerations of X and Y </li></ul><ul><li>What is special about the acceleration of X? Explain it’s journey… </li></ul>4.0 8.0 X = 2 m/s 2 Y = -2.5 m/s 2 10.0 5.0 7.5 12.5 15.0 17.5 Velocity Y 6.0 2.0 0.0 - 2.0 Velocity X 6 5 4 3 2 1 Time
19. 20. Homework Questions <ul><li>Page 70, Qs 5 - 8 </li></ul>
20. 21. Vectors and Scalars <ul><li>Spot the vectors among the scalars </li></ul>5 m/s 16 m due North - 17 m/s 2 16 Newtons 7 N 67 m/s 12 seconds Weight 94 Joules
21. 22. Learning Intentions <ul><li>By the end of the lesson we will be able to… </li></ul><ul><li>Construct a distance-time graph to represent motion </li></ul><ul><li>Identify common shapes of a d-t graph </li></ul><ul><li>Use a d-t graph to calculate an unknown speed </li></ul>
22. 23. Distance – Time Graphs <ul><li>This is a visual way of representing motion by using a graph. </li></ul>
23. 25. Distance- Time Graphs Distance (m) Dist. Straight line, positive correlation, both increase at the same rate
24. 26. Distance- Time Graphs Distance (m) Dist. Curves up, as seconds pass, the car covers more distance than the second before
25. 27. <ul><li>Distance -Time graph (Pg 71) </li></ul><ul><li>Some of the common shapes that describe the motion of an object are- </li></ul>Graphs of motion speed speed speed Increasing speed Decreasing speed
26. 28. <ul><li>Page 73 in CCEA </li></ul><ul><li>Question 10 (answer in full!) </li></ul>
27. 29. Learning Intentions <ul><li>By the end of the lesson we will be able to… </li></ul><ul><li>Identify common shapes of a d-t graph </li></ul><ul><li>Use a d-t graph to calculate an unknown speed </li></ul><ul><li>Recognise the link between the gradient of a d-t graph for an object and the motion of that object </li></ul>
28. 30. <ul><li>The word ‘gradient’ is used to explain the shape of the line on the graph </li></ul>1 3 2 5 4 <ul><ul><li>Match the phrases to the correct graphs </li></ul></ul>
29. 31. <ul><li>A value for the gradient of a graph can be calculated by dividing the change in the ‘y value’ by the change in the ‘x value’ </li></ul>0 15 75 y x 1.2 4.8 y x 0 Gradient = 75 / 15 = 5 Gradient = -4.8 / 1.2 = -4 Negative gradient, slope down
30. 32. The change in y is the distance the object has travelled The change in x is the time the object was travelling Speed equals distance divided by time, therefore the gradient of the graph is the same as the speed of the object
31. 33. What is the gradient, and hence the speed of the car? Change in y = Distance travelled = 800 – 200 = 600 m Change in x = Time taken = 36 - 16 = 20 s Gradient = Speed = Distance / Time = 600 / 20 = 30 m/s
32. 34. Learning Intentions <ul><li>By the end of the lesson we will be able to… </li></ul><ul><li>Identify common shapes of a v-t graph </li></ul><ul><li>Use a v-t graph to calculate an unknown acceleration </li></ul><ul><li>Recognise the link between the gradient of a v-t graph for an object and the motion of that object </li></ul>
33. 35. <ul><li>We’ve seen how Distance-Time graphs can be a clear illustration of an object’s motion. Another usefully way to present this motion is in the form of a Velocity- Time graph. </li></ul>
34. 36. Felix is bonkers…
35. 38. <ul><li>Velocity -Time graph </li></ul><ul><li>Some of the common shapes that describe the motion of an object are- </li></ul>Graphs of motion speed speed speed Increasing speed Decreasing speed Acceleration Constant speed Slower Acceleration Stopped Deceleration v v v v v v t t t t Slower constant speed
36. 39. <ul><li>For a Distance-Time Graph the gradient at any instant represents the speed </li></ul><ul><li>- eg. Zero (flat) gradient means no speed </li></ul><ul><li>For a Velocity-Time Graph, the gradient at any instant represents the acceleration </li></ul><ul><li>- eg. Steep (high) gradient means large acceleration </li></ul>
37. 40. Learning Intentions <ul><li>By the end of the lesson we will be able to… </li></ul><ul><li>Calculate displacement from a v-t graph </li></ul><ul><li>Recall what is meant by an object’s momentum </li></ul><ul><li>State the equation for momentum and solve simple problems related to momentum </li></ul>
38. 41. <ul><li>Consider this example- A car travels at 4 m/s for 10 s </li></ul><ul><li>Velocity / Time graph for the motion </li></ul>Time (s) Velocity (m/s) 4 10 Wee Bit Extra
39. 42. Time (s) Velocity (m/s) 4 10 Velocity = Displacement / Time Area under the graph!! From the graph- Velocity = 4 m/s Time = 10 s Re-arrange the equation- d = v x t = 4 x 10 = 40 m v d t
40. 43. <ul><li>For a Velocity-Time graph the displacement can be calculated by finding the area under the line </li></ul>Displacement
41. 44. <ul><li>What is the total displacement of each of the object’s motion illustrated in the graphs below- </li></ul>Examples t V 15 200 t V 5 16 8 Area under line = 15 x 200 Displacement = 3000 m Area under line = (5 x 8) + (0.5 x 8 x 5) Displacement = 60 m
42. 45. Try this one… <ul><li>Pg 74 </li></ul><ul><li>Questions 13 (Ignore the last sentence in Q13 about the ‘graphical method’) </li></ul>
43. 46. Momentum <ul><li>The Superhero factor! </li></ul>verses
44. 47. Momentum <ul><li>If an object is moving then it has momentum. This can be calculated by using the equation- </li></ul><ul><li>Momentum = Mass x Velocity </li></ul><ul><li>p = m x v </li></ul><ul><li>kgm/s = kg x m/s </li></ul><ul><li>Momentum is a vector quantity </li></ul>
45. 48. Example <ul><li>What is the momentum of i) the car, ii) the motorcycle? </li></ul><ul><li>Which would have more momentum if they were both travelling at the same velocity, why? </li></ul>30 5 Velocity (m/s) 200 1000 Mass (kg) Motorcycle Car
46. 49. <ul><li>Momentum = mass x velocity </li></ul><ul><li>p = m x v </li></ul><ul><li>- For the car </li></ul><ul><li>p = 1000 x 5 = 5000 kgm/s </li></ul><ul><li>- For the motorcycle </li></ul><ul><li>p = 200 x 30 = 6000 kgm/s </li></ul><ul><li>If they were both travelling at the same speed the car would have the most momentum as it has the most mass </li></ul>30 5 Velocity (m/s) 200 1000 Mass (kg) Motorcycle Car