1 / 30

Motion Graphs

Motion Graphs. Distance and Displacement. Distance is a scalar quantity! is how far something has moved. is measured in metres etc. Displacement is a vector quantity. is how far an object has moved from its starting point and in what direction.

savea
Download Presentation

Motion Graphs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Motion Graphs

  2. Distance and Displacement

  3. Distance • is a scalar quantity! • is how far something has moved. • is measured in metres etc. • Displacement • is a vector quantity. • is how far an object has moved from its starting point and in what direction. • measured in metres but also has a direction. • is the (straight line) distance between 2 points with the direction given too!

  4. If the bear skis the 7 metres to the tree then back to the start and then all the way to the house, what distance would he have gone? _______m

  5. What would his displacement from the starting point be ? ___________ m in an easterly direction.

  6. Speed and velocity

  7. Speed is a scalar quantity! • It is how fast something has travelled • It is measured in metres/second or km/hour. • Velocity is a vector quantity. • This is how fast and in what direction something travels IN A STRAIGHT LINE!!! • This is measured in m/s or km/h but also has a direction.

  8. Speed • If a car travels 150 km in 2 hours then calculate the average speed of the car: Average Speed = distance travelled/ time = d/t = 150 km/ 2 h = 75km/h Or write it like this: = 75 km h ⁻¹

  9. Velocity • If a plane travels 480 km in a southerly direction for 2 hours then calculate the average velocity of the plane: Average velocity= distance travelled in a straight line time Vav = s/t = 480 km/ 2 h South = 240km/h South Or write it like this: = 240 km h ⁻¹ South

  10. Remember that if an object is going at a constant speed but changes direction (turns) then its velocity changes!!

  11. All these abbreviations – what do they stand for???!!! d = distance s = displacement t = time v= velocity or final velocity u = initial velocity a = acceleration

  12. Motion graphs It is often easier to show the motion of an object with a graph rather than with words. There are 2 types of graph we will look at: • Displacement – time graphs or distance – time graphs. • velocity - time graphs or speed- time graphs. VELOCITY (v)is simply speed in a given direction DISPLACEMENT (s) is the distance in a given direction

  13. With both types of graph, time is plotted on the x axis. • The further to the right along the x axis we go – the longer the time from the start! • Velocity, distance etc are always plotted on the y axis. • We assume the initial direction of motion to be positive.

  14. Distance (m) 0 1 2 3 4 5 6 7 8 9 10 11 A body at rest. That is it is stopped or standing still! 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  15. An object moving at constant speed. Constant speed because the lines are straight! Which line shows the object going fastest? Distance (m) 0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  16. Speed is given in m/s so we can work out the speed here by saying speed = rise/run = distance/time. Work it out for each. Distance (m) 0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  17. A body accelerating! You can see that the speed is increasing: the distance travelled is more each second so this shows it is accelerating!! Distance (m) 0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  18. Lets look at an example: First we will give the information in words then as a displacement – time graph. Matthew starts from point A and travels at 2m/s for 3 seconds to point B. He then stops at point B for 4 seconds before going back towards point A at an initial velocity of -1.5m/s for 2 seconds then stopping at an intersection for 1 second before continuing to point A at -1.5 m/s. Ok – lets look at this graphically!!!!!

  19. Much Easier than words!!! Distance (m) 0 1 2 3 4 5 6 7 8 9 10 11 Matthew’s trip 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  20. Lets do some questions! 

  21. This axis has SPEED not distance on it!!!! What is the difference between this graph and the ones we looked at before?? Speed (m/s) 0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  22. So what does this graph show? Speed (m/s) 0 1 2 3 4 5 6 7 8 9 10 11 It shows that the object is moving at a constant speed of 5.5m/s 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  23. What does this graph show? Speed (m/s) 0 1 2 3 4 5 6 7 8 9 10 11 It shows that the objects’ speed is increasing or the object is accelerating! 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  24. What does this graph show? Speed (m/s) 0 1 2 3 4 5 6 7 8 9 10 11 It shows that the objects’ speed is decreasing or the object is decelerating! 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  25. Which line shows faster acceleration? Green or blue? Acceleration = speed/time so Blue = 3m/s/s Green = 1m/s/s Steeper slope = faster acceleration! Speed (m/s) 0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  26. Putting it all together: Speed (m/s) 0 1 2 3 4 5 6 7 8 9 10 11 Steady speed Fast deceleration Or negative acceleration Fast accn Slow accn 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  27. What other information can we get from displacement – time and speed time graphs? Speed (m/s) 1 2 3 4 5 6 7 8 Distance (m) 10 20 30 40 50 60 1 2 3 4 5 6 7 8 9 Time (s) 1 2 3 4 5 6 7 8 9 Time (s) Gradient = rise/run = 7/7 = 1m/s/s = acceleration!!! Area under the graph = ½ time x speed = s x m/s = m = distance travelled!!! Gradient = rise/run = 30/6 = 5m/s = speed!

  28. Lets look at the last example and work out the distance travelled.

  29. Work out the area under the line to work out the distance travelled Speed (m/s) 0 1 2 3 4 5 6 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 12 time (s)

  30. Reading – Pages 3 to 4 Can you stick the sheet in too?

More Related