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What is the answer for question 1. a) http://postimg.org/image/f1kxxqprl/

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lkballer24 | Student, Grade 11 | Valedictorian

Posted April 15, 2013 at 8:20 PM via web

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What is the answer for question 1. a)

http://postimg.org/image/f1kxxqprl/

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mlehuzzah | Student , Graduate | (Level 1) Associate Educator

Posted April 16, 2013 at 2:49 AM (Answer #2)

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Speed = Distance / Time

In other words, speed is the slope of your distance graph.  So the question is just asking: "What is the slope of the graph at each moment in time?"

 

So for example:
at time 0, the distance is 10
at time 15, the distance is 25
so the slope is (25-10)/(15-0)=15/15=1
(I'm not sure what the units are; I can't really read the picture that well.  I'm guessing it is 1 meter/second, or 3.6 km/ hour, or about 2.2 miles / hr)

 

at time 15, the distance is 25
then at time 25, the distance is 65
so the slope is (65-25)/(25-15)=40/10=4

at time 25 the distance is 65
at time 30, the distance is still 65
so the slope is (65-65)/(30-25)=0

finally, at time 30, the distance is 65
at time 40, the distance is 0
so the slope is (0-65)/(40-30)=-6.5

the speed here is actually positive 6.5

some explanation.  Let's say I stand in one place.  And you are standing 65 m away from me.  And in 10 seconds, you are now in the same place as I am.  Then you went from being 65 m away, to being 0 m away.  So your distance from me change by -65 m.  But you ran a distance of 65 m, not a distance of -65.

So, the graph would look like:

 

Note the open circles: the speed isn't actually defined at those spots.  At the very instant when t=15 seconds, and you instantaneously change from going 1 m/s to 4 m/s, at that moment, the speed isn't defined

 

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lkballer24 | Student , Grade 11 | Valedictorian

Posted April 16, 2013 at 11:13 AM (Answer #3)

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Is this how the graph for 1.a) should look like, because if so there is supposed to be 2 graphs for 1.a).

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