Question

Distance-Time Graph Question! (MEDAL)

A motorist left town X at 08 00 for town Y, situated 120 km away, travelling at a constant speed v km/h, so as to arrive at Y at 10 40. But after travelling for 80 minutes, his car developed engine trouble and he had to stop for 30 minutes to repair it. Then he continued his journey at a speed of u km/h, so as to arrive at Y ar 10 40.

(a) Sketch the distance-time graph of the car.
(I DID THAT ALREADY) [attached]

(b) Calculate the values of v and u.
(found "v" but had trouble with "u". plz explain how to find both again)

Answer 1

is the answer of speed u ..is 50km/h ??

Answer 2

I know both the answers. Don't know how!

Answer 3

firstly the value of v would be 45km/h ryt .?

Answer 4

YEA

Answer 5

That was easy! But can't find u

Answer 6

he travelled for 80 minutes...with speed v...that means he travelled \[\frac{ 4v }{ 3 }km\]

Answer 7

which is by putting the value as 45 ...we get ...60 km ..!

Answer 8

that means after 60km his car got trouble ...he waited 1/2 an hour ..! then started.

Answer 9

no no ..~! why 59 /...60 only ..?

Answer 10

Oh yea, it's 60 km...

Answer 11

actual journey will take 8/3 hours ...but he wasted ..110 minutes ..till now which is 11/3 hourse ..

Answer 12

that means ..now he has to reach his destination ...in 5/6 hours ...right .?\[\frac{ 8 }{ 3}-\frac{ 11 }{ 6 } =\frac{ 5 }{ 6 }\]

Answer 13

so remaining 60 km must be covered in 5/6 hours ...so the speed u must be 60 divided by 5/6 which is ..72km/h ...sorry ...i was wrong in the beginning ..but u=72

Answer 14

OmG! That's the right answer! But u did that using calculations. How to find this value using the graph?

Answer 15

How do I find the speed using this information?

Motorist starts journey at = 09 50
Motorist Journey ends at = 1040
Journey Distance = 60 km

Answer 16

umm ...an attempt ..try using the slope concepts.?

Answer 17

Well, I am doing the "Kinematics" so it's about Graphs...

What do I do first?

Speed = Distance/Time

Speed = 60/Time

How to find time?

Answer 18

1040 - 0950?

Answer 19

some how u need to get time as 5/6 hours ..which is 50 minutes ...

Answer 20

yes u were right ..

Answer 21

The time between 0950 and 1040 is 50 mins?

Answer 22

yes ..so u are der ..u have done that !

Answer 23

How do I find time using this Graph?

Answer 24

Oh wait! I found the time! WTF

Answer 25

Hmm dunno how but did somehow! Thanks!

Answer 26

apply slope as y2-y1/x2-x1

Answer 27

my medal ....???

Answer 28

gave it already...

Answer 29

U didn't got?

Answer 30

lol ..thank u