Distance-Time Graphs

Features of Time-Distance Graphs
Graphs comparing distance and time should be called Time-Distance graphs because:


Calculating the Speed


Example - Hydrocopter Rescue

Hydrocopter

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:

LEGTIMEDISTANCE
1st (land)12 min12 km
2nd (water)10 min20 km
3rd (rescue)5 min0 km
4th (water)12 min20 km
5th (land)14 min12 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):

LEGTIMEDISTANCESPEED
1st (land)12 min12 km12 ÷ 12 = 1 km/min
2nd (water)10 min20 km20 ÷ 10 = 2 km/min
3rd (rescue)5 min0 km0 km/min (not moving)
4th (water)12 min20 km20 ÷ 12 =1.7 km/min
5th (land)14 min12 km12 ÷ 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 TIMEDISTANCE FROM BASE
0 min0 km
12 min12 km
22 min32 km
27 min32 km
39 min12 km
53 min0 km

Hydrocopter graph