Problem with choosing which axis should be positive or negat

In summary, the tension in the rope does not affect the choice of positive or negative direction in a problem, as long as it remains consistent throughout. If you choose opposite directions compared to someone else, your answer will be the negative of theirs.
  • #1
Frankenstein19
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Homework Statement


A 14.0kg bucket is lowered vertically by a rope in which there is 163N of tension at a given instant. What is the acceleration of the bucket.

Homework Equations


ƩF = may

The Attempt at a Solution


I know how to solve this but I got it wrong because of the signs.
Since the bucket was being lowered I thought that downward was going to be positive, but the correct solution says that up is positive; WHY?
 
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  • #2
It doesn't matter what you choose to be positive or negative. If you chose differently than the book, then your signs will be opposite at the end. That's it. As long as you're consistent, it'll be the same.
 
  • #3
axmls said:
It doesn't matter what you choose to be positive or negative. If you chose differently than the book, then your signs will be opposite at the end. That's it. As long as you're consistent, it'll be the same.
so even though its negative it's correct? or are you saying i wasnt consistent with my signs and that regardless of what i choose to be positive or negative that as long as I am consistent with it that i should get the correct answer?
 
  • #4
If your answer is the negative of the correct answer, and you chose opposite axes as the correct answer, then your answer is also right. Yes, you can choose your positive direction to be whatever direction you want as long as it stays the same throughout the problem.

You'll get the correct answer for those axes. If you chose your positive direction to be the opposite direction as someone else, that just means your answer will be the negative of theirs.
 
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  • #5
axmls said:
If your answer is the negative of the correct answer, and you chose opposite axes as the correct answer, then your answer is also right. Yes, you can choose your positive direction to be whatever direction you want as long as it stays the same throughout the problem.

You'll get the correct answer for those axes. If you chose your positive direction to be the opposite direction as someone else, that just means your answer will be the negative of theirs.
ohh ok thank you so much!
 

1. What is the problem with choosing which axis should be positive or negative?

The problem with choosing which axis should be positive or negative is that it can lead to confusion and inconsistencies in data analysis and interpretation. If the wrong axis is designated as positive, it can result in incorrect calculations and conclusions.

2. How do I determine which axis should be positive or negative?

The choice of which axis should be positive or negative depends on the specific situation and the variables being measured. In general, it is best to designate the axis that represents the independent variable as positive, and the axis that represents the dependent variable as negative.

3. Can I change the designated positive and negative axes after collecting data?

Yes, it is possible to change the designated positive and negative axes after collecting data, but it is not recommended. Doing so can result in confusion and inconsistencies in data analysis and interpretation. It is best to determine the positive and negative axes before collecting data and stick to that designation throughout the analysis.

4. What happens if I accidentally designate the wrong axis as positive?

If the wrong axis is designated as positive, it can result in incorrect calculations and conclusions. It is important to carefully consider which axis should be positive and negative before collecting data to avoid this mistake.

5. Are there any exceptions to the general rule of designating the independent variable as positive and the dependent variable as negative?

Yes, there are certain situations where the general rule may not apply. For example, in some cases, both variables may be equally dependent on each other, and it may not matter which axis is designated as positive or negative. It is important to carefully consider the specific situation and variables before making a decision about which axis should be positive or negative.

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