#1**+13 **

Best Answer

Total distance is 0.5*5*30+|0.5*-20*15| = 75+150 = 225m

Total displacement = 0.5*5*30+(0.5*-20*15) = 75-150 = -75m

Melody
Sep 26, 2014

#2**+3 **

yes your answer is correct but I don't understand why you take 15 !! why not 20

in this step !

0.5*5*30+|0.5*-20*15|

xvxvxv
Sep 26, 2014

#6**+10 **

I am going to add this as an interest question so I thought I would comment a little further.

The vertical axis is m/s the horizontal axis is seconds.

When you multiply these together the seconds cancel out and you are left with metres which is distance.

When you find the area of a rectangle it might be metres * metres so the units will be m^2

When you find the area under these lines the units are m/s and seconds so the resultant unit is metres.

**That is why you can find the distance travelled by finding the area under the curve.**

If you have any comments or questions please post here. This is a really interesting and important concept.

Melody
Sep 26, 2014

#7**+5 **

Thanks for that explanation, Melody...I don't "do" Physics but I see what you are talking about.....!!!!

CPhill
Sep 27, 2014

#9**+10 **

Actually, now that i look at the actual graph it is really weird.

How can you go from +30m/s to -20m/s in an instant. Maybe it is in a different universe?

what I said before still goes though.

Melody
Sep 27, 2014

#10**0 **

Ninja has asked a question.

"This distance/displacement question does looks interesting.

I understand the steps to solve and the other numbers, but where do you get 0.5 from?"

--------------------------

What I needed to find was the area between the curve (line) and the time (horizontal) axis.

The shape of this area is a triangle so I used the formula for the area of a triangle, THAT is where the 0.5 came from.

--------------------------

Maybe you could do a one off Ninja and pop this into the great answers to learn thread and pop it in under Physics? If you don't it doesn't matter.

Melody
Sep 28, 2014