Coulomb’s Law: Pesky Negative Signs!

[justadream]

TPR SW Physics #248

“Two particles of opposite charge are moved slowly apart. As the particles are moved apart, the force between them is_______”


Answer: Attractive and decreasing

My answer: Attractive and INCREASING



F = kqq/r^2

Since one charge is positive and one is negative, the force is always negative (this is how TPR defines in their own content books)



As r increases, the force gets less negative (so the force is increasing – getting closer to 0).



Isn’t this question somewhat ambiguous since it doesn’t mention magnitude….?

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[Cawolf]

You need to remember that F = kqQ/r^2 r(hat). Force is a vector. So that negative sign indicates direction.

The force is always negative in the fact that they attract and decrease the distance between them. It is important to note that no matter the sign, the electrostatic force will decrease by 1/r^2.

 

[exacto]

Forget all the formulas and text, just look at the logical answer...

You have to opposing charges which will be drawn to each other...like you said and got right) and as you increase the distance, the only logically answer would be that the forces are lessening (decreasing). It wouldn't make sense if the forces increased spontaneously.