Features of Time-Distance Graphs
Graphs comparing distance and time should be called Time-Distance graphs because:
Calculating the Speed
A hydrocopter is a rescue vehicle has an aircraft engine and a catamaran hull (two hulls). It is amphibious (can travel over water or land/snow/ice).
The legs of a recent rescue journey are as follows:
LEG | TIME | DISTANCE |
1st (land) | 12 min | 12 km |
2nd (water) | 10 min | 20 km |
3rd (rescue) | 5 min | 0 km |
4th (water) | 12 min | 20 km |
5th (land) | 14 min | 12 km |
(a) Calculate the hydrocopter's speed (in kilometres per minute) at each of the five stages of the journey. Write the speed information in a table.
(b) Draw a distance-time graph showing all the legs of the journey.
Answer (a):
LEG | TIME | DISTANCE | SPEED |
1st (land) | 12 min | 12 km | 12 ÷ 12 = 1 km/min |
2nd (water) | 10 min | 20 km | 20 ÷ 10 = 2 km/min |
3rd (rescue) | 5 min | 0 km | 0 km/min (not moving) |
4th (water) | 12 min | 20 km | 20 ÷ 12 =1.7 km/min |
5th (land) | 14 min | 12 km | 12 ÷ 14 = 0.9 km/min |
Answer (b):
Because the time-distance line graph requires a cumulative total of time on the x-axis and distance from the base on the y-axis, a new table is needed.
CUMULATIVE TIME | DISTANCE FROM BASE |
0 min | 0 km |
12 min | 12 km |
22 min | 32 km |
27 min | 32 km |
39 min | 12 km |
53 min | 0 km |
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