Acceleration vector exercise (coordinate system)

AI Thread Summary
The discussion revolves around solving an acceleration vector problem using the coordinate system. Initially, the participant miscalculated the vector subtraction, leading to confusion about the correct answer. After receiving clarification, they correctly identified the first choice as the solution by accurately subtracting the vector components. The conversation emphasizes the importance of understanding the problem rather than relying solely on multiple-choice strategies. Ultimately, the correct approach involves careful calculation of both i and j components to arrive at the right answer.
sdadksajd
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Homework Statement



Please read the attachment =)

All the formulas I was given are also on a separate attachment

I initially thought the answer was the last one because I did rf-ri and subtracted across and got 0 mi + 25mj but I am not sure =[

Homework Statement

 

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sdadksajd said:

Homework Statement



Please read the attachment =)

All the formulas I was given are also on a separate attachment

I initially thought the answer was the last one because I did rf-ri and subtracted across and got 0 mi + 25mj but I am not sure =[

Homework Statement


rf-ri sounds like a good idea, but 0 mi + 25mj isn't the answer to that.

ri has a 50mi term
rf has a -50mi term

so when you subtract them the answer will not be zero [since they are different]
 
Oh thanks for the much needed advice. I redid the problem and got the first choice as my answer which was from subtracting -25 from 25 and 125 from 100. Can anyone verify that choice a is correct =[]
 
sdadksajd said:
Oh thanks for the much needed advice. I redid the problem and got the first choice as my answer which was from subtracting -25 from 25 and 125 from 100. Can anyone verify that choice a is correct =[]

My previous post should have said 25mi and -25mi - you can't look at "pictures" and respond at the same time.

While the first option is correct - the description of what you did is all backwards.

You actually subtracted 25 from -25, and subtracted 100 from 125.
 
Thanks a ton peter I understand now :)
 
sdadksajd said:
Oh thanks for the much needed advice. I redid the problem and got the first choice as my answer which was from subtracting -25 from 25 and 125 from 100. Can anyone verify that choice a is correct =[]

By the way: applying the logic of multiple choice questions leads you to this answer.

If you consider just the i components.

If you add them [or subtract poorly], you get 0i [only one option has this].

If you subtract the second from the first you get 50i [only one option has this]

If you subtract the first from the second you get -50i [two options have this]

If the answer was not one of the -50i ... examples, you would not even have to consider the j component - possible but unlikely.

consider the j component. when you subtract here, you either get 25j or -25j

only one of those possibilities is offered - and there is your answer!

Playing the multiple choice game rather than understanding the problem is not a recommended technique - but if all else has failed it is useful.
Remember: with a normal problem you are trying to find the answer; with a multiple choice question you are only trying to identify which of the options is the answer.
 
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