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:
|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.
|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|
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|