Motion in One Direction - Motion Graph and Diagram.pptx

Grade 7 Science: Motion in One Direction/Motion Graph and Diagram

1. Motion Graph and Diagram

2. Graph Diagram

3. Describing the motion of an object is easier understood through graphical presentations or use of diagrams .

4. Herein , the relationship of distance and time, speed or velocity and time are interpreted easily when presented through graphs and diagrams.

5. Distance-Time Graph ( d-t graph) One way of describing motion is by plotting distance against time in a Cartesian plane. Like in your mathematics class, this presentation will make use of X and Y axis.

6. Distance-Time Graph ( d-t graph) Time is plotted on the X-axis. The further to the right on the axis, the longer the time from the start. Distance is plotted on the Y-axis. The higher up the graph, the further from the start.

7. Objects is at Rest An object is NOT MOVING when a horizontal line is shown on a distance-time graph. In this case, time is increasing to the right , but the distance remains the same . The object is not moving hence , the object is At Rest .

8. Object Moving at Constant Speed An object is moving at a constant speed when the distance covered increases constantly with time . Constant speed is shown by straight lines on a graph.

9. Suppose we have two moving objects: Both of the lines in the graph show that each object moved the same distance , but the steeper dashed line got there before the other one:

10. Steeper Line The steeper dashed line indicates that the object has moved a greater distance at a given time. In other words , it has higher speed than the object which is represented by the solid line. Both lines are straight, so both speeds are constant.

11. Below is a graph that show acceleration. It looks different from those that show constant speed. The line on this graph is curving upwards . This shows an increase in speed since the line is getting steeper. In other words, the object is accelerating .

12. Speed-Time or Velocity-time Graph (V-T Graph) Another type of motion graph is the velocity-time graph . The velocity of the object is plotted against time. Although it looks much like distance-time graphs, the slope of the graph describes the acceleration of the object .

13. Object Moving at Constant Speed The figure shows an object moving at a constant speed. A straight horizontal line means that speed is constant . It is not changing over time. A straight line, in this case , does not mean that the object is at rest. Remember , this is a v-t graph.

14. Object is Accelerating (Speeding Up) The moving object is said to be ACCELERATING when its speed is increasing as shown in the graph.

15. Object is Decelerating (Slowing Down) the moving object is decreasing its speed or slowing down. Thus, the moving object is DECELERATING.

16. DIAGRAMS Another method of describing motion is through the use of diagrams . A ticker-tape diagram is an example of motion diagram. This is sometimes called as dot diagram which makes use of a stationary " ticker" that marks the tape at regular time intervals.

17. A dot diagram reveals if the object is moving with a constant velocity or accelerating .

18. A changing distance between dots indicates a changing velocity and thus accelerating.

19. A constant distance between dots represents a constant velocity and therefore no acceleration. Dot diagrams for objects moving with a constant velocity and with an accelerated motion are shown below.

20. Let Us Practice!

21. Imagine a car with an engine leak that drips oil at a regular rate. As the car travels through town, it would leave a trace of oil on the street. That trace would reveal information about the motion of the car.

22. Glen owns such a car and it leaves a signature of Glen’s motion wherever he goes. Analyze the three traces of Glen’s ventures as shown below . Assume Glen is traveling from left to right. Describe his car’s motion characteristics during each section of the diagram

23. a. What happens to the car’s speed in section A? b. Infer the car’s motion at section B. c. Describe the car’s motion in section C.

24. Glen decelerates from a high speed to low speed until he is finally stopped. He remains at rest for a while and then gradually accelerates until the trace ends.

25. Describe the car’s motion for Sections : A? B?

26. Glen travels at a constant speed during the first time interval and then gradually accelerates until the trace ends.

27. Describe the car’s motion for Sections : A? B? C? D?

28. Glen moves with a constant speed in the first time interval. He then abruptly decelerates to a stop. He remains at rest for some time and then moves with a constant speed, slower than the first speed.