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Lees75

Vector help

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Lees75

DS16 and I are puzzling over a spec maths question and despite getting a great spec maths mark when I did it, that was a LONG time ago, and I haven't used it since.

 

Basic summary of the question - Car has travelled with a velocity vector of [18,24] km/hr for 30 mins, so position ends up at 9, 12.

 

Then car travels with a new velocity vector of [24,14] km per hour until they reach position [18, y]

 

So, we need to work out what time they reach 18, y, so to work "y", we are going to use the slope of the line, but are not sure if the [24,14] should be from the starting point of [0,0] or is it from the [9,12], if that makes sense? DS16 has asked his class-mates and various ones have done it each way.

 

I said I would ask EB, because there are some great maths minds. DS16 thanks you in advance!!!!

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BusbyWilkes

This is in the managing money forum. You might want to change it!!

There is currently great math debate in the keeping your kids home from school topic. Put this one in there and blow their minds.

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GingerbreadWoman

It should be from the ‘new’ starting point. The line with the second vector won’t go through (0, 0).

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Nasty Teens
Posted (edited)

You know the time the car reached 9,12. Calculate the new time from this known point.

 

A real life example. I traveled from Sydney to Canberra on this vector for this period/at this speed. I then travelled from Canberra to Adelaide ect. The vector isn't Syd o ADL it is Syd (0,0) to can to adl.

Edited by Nasty Teens
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FeralRebelWClaws

Yep what Gingerbread woman says.

 

[9,12] becomes the new origin of the second vector, it is the starting point of the new vector.

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Lees75
Posted (edited)

It should be from the ‘new’ starting point. The line with the second vector won’t go through (0, 0).

Thank you, thank you, thank you. That is what I was trying to tell him, but he wasn't convinced I was right.

 

When I put it in the concept of heading north, south, east and west from different starting points, he could see what I meant, but still wasn't sure I was right.

 

ETA - not sure how I ended up in the Managing Money forum - I haven't been in here for ages!

Edited by Lees75

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Sincerely
Posted (edited)

Agree with everyone else's advice.

 

y = 17.25

 

It took 22.5 mins to get to [18,17.25]

 

Happy to provide workings if needed but your proposed strategy to solve this problem seems appropriate, so you've probably got this.

Edited by Sincerely
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