Time Intervals and Position Time Graphs

1
Time IntervalsandPosition Time Graphs

• Science 10

2
Time and Time Intervals

• In physics, we will often start timing when
  something occurs (this provides a zero in time)
• We may also consider a time interval which is
  symbolized as ?t

3
Position-Time Graph

• A position-time graph is one that generally has
  position on the y-axis and time on the x-axis
• We will normally use metres for position and
  seconds for time

4
Gebrselassie

• At the Berlin Marathon in 2008, Ethiopian Haile
  Gebrselassie set a new world record for the
  marathon with a time of 20359. The key to
  Gebrselassies success is his ability to maintain
  a constant pace through out the event. His split
  times for each 5000m interval (and half marathon
  and marathon splits) are given below.

d(km) t(s)
0 0
5 875
10 1753
15 2643
20 3530
21.1 3725
25 4421
30 5307
35 6185
40 7054
42.2 7439
5

1. Using the data table, plot his position (d) on
   the y-axis and his time (t) on the x-axis.
   Ensure that you choose a scale that will enable
   you to use as much of the graph paper as
   possible.
2. Using the data, draw a line of best fit to the
   data and determine the slope of the line. What
   are the units for the slope in this instance?
3. For each 5km split (you can ignore the 21.1km and
   42.2km) calculate his average speed in m/s by
   dividing the distance in metres by the time in
   seconds.
4. Compare the results for each segment in part 3
   with the result for part 2. What do you notice?
   What you can say about his pacing?