# displacement-time graphWatch

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Thread starter 4 years ago
#1
Hey guys .
A quick question .
A police car joins a straight motorway at junction 4 and travels for 12km at a constant speed for 400s and then leaves at junction 5 and rejoins the opposite direction and travel for 8km at a constant speed for 320 s to reach the scene of an accident .
i've calculated the displacement of the car which is 4 but have no clue how to draw a displacement-time graph for it, any help would be much appreciated .
0
4 years ago
#2
(Original post by Alen.m)
Hey guys .
A quick question .
A police car joins a straight motorway at junction 4 and travels for 12km at a constant speed for 400s and then leaves at junction 5 and rejoins the opposite direction and travel for 8km at a constant speed for 320 s to reach the scene of an accident .
i've calculated the displacement of the car which is 4 but have no clue how to draw a displacement-time graph for it, any help would be much appreciated .
I take it you mean 4km from junction 4?

The displacement graph uses time along the x-axis, and displacement from the starting point (origin) along the y-axis.

The car will reach a maximum displacement (12km) from the start (origin) at 400 seconds. So draw a straight line from the origin to the co-ordinates (400s, 12km).

The car then travels back towards the start, reaching 12km - 8km = 4km another 320 seconds later.

i.e. 400 + 320 = 720 seconds in total from the start. So draw a second straight line from co-ordinates (400s, 12km) to co-ordinates (720s, 4km).

Viola, displacement graph completed.
0
Thread starter 4 years ago
#3
thank you so much i get it now
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