Sam asked in Science & MathematicsPhysics · 3 months ago

Shouldn't 20N forwards be +20N not -20N. Correct me if I'm wrong because this is what the textbook question says ?

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• 3 months ago
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Don't overthink this one. It doesn't relate to vector mechanics

or Mathematics in general.

If the forward direction is arbitrarily minus, then the reverse

direction is positive by convention.

Answer: +80N.

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Thank you for choosing a best answer.

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• 3 months ago

You can define your positive direction any way you want. If forwards is negative, then backwards is positive.

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• 3 months ago

Do you think north should be up on a map? Because those two questions are equivalent.

Here's how you do vectors. 20 N in one direction is different from 20 N in the opposite direction so we make the distinction by choosing a positive direction.

A vector pointing in the positive direction is positive. A vector pointing in the opposite from positive (negative) direction is negative.

In your problem, "backwards" is chosen as the positive direction. Forwards is chosen as the negative direction.

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• Anonymous
3 months ago

+80 N , what else ??

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• Anonymous
3 months ago

+ and - directions are whatever you define them to be.

For east-west motion, we usually say east is positive.  In this case, if your car faces west and you push it forwards, then you are pushing it in the negative direction.

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• 3 months ago

You can define positive any way you please AS LONG AS YOU ARE CONSISTENT. For this problem they have already defined forwards as negative therefore backwards MUST be positive for consistency.  Repeat there is no right and wrong for the positive direction.  Consistency is the only consideration.

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