Question

A plane travels 200km at 150 km/h, 300km at 200 km/h and 400km at 250km/h all at a constant speed.

draw a distance time graph to represent the journey
hence estimate the average speed for the entire journey ​

Answer 1

`\leq`Answer:

Explanation:

The distance, D, is given by the speed, S, times the time, T:

D = S*T

D S*T Time Equation for each segment

200 = 150T1 T1 = 1.33 hr y=150x 0
`\leq` T
`\leq` 1.33 hr

300 = 200T2 T2 = 1.5 hr y=200x 1.33
`\leq` T
`\leq` 2.83 hr

400 = 250T3 T3 = 1.6 hr y=400x 2.83
`\leq` T
`\leq` 4.43 hr

The graph can be drawn as three lines, ione each for the three segments, each having the slope shown in the equation for that segment and extending between the range of values for T (which is the "x" in the equation and on the graph). The y axis will be ditance, in km.

The overall speed is the total distance divided by the total time:

D(km) T(hr)

1) 200 1.33

2) 300 2.83-1.33 = 1.5

3) 400 4.43-2.83 = 1.6

900 km 4.43 hr

(900 km)/(4.43 hr)

Average speed = 203.01 km/hr