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Hi there,

I am slightly confused about how to answer the following question:

"The diagram below shows a window-cleaning device that can be used to clean both sides of the glass at the same time. It consists of two plastic holders with bar magnets inside, and a cleaning material attached two the outside.

When the inner part of the device A is moved across the inside surface of the window, the outer part B follows it, moving over the outer surface of the window.

Explain why B follows the movement of A"

The answer to this question states:

"The opposite (N+S) poles are attracting one another and if (in picture) A is moved upwards its S pole will also resist the upward movement of B by repulsion. So B follows A."

I am a bit confused about this answer, isn't the inner part of the magnet A attracted to the outer part of magnet B? Why is it talking about repulsion, and how would that make the two magnets follow each other?



1 Answer 1


I think what they meant to say is that if you move the A magnet up, it's S pole will get nearer to the magnet B S pole, therefore creating a repulsion which moves the magnet B up aswell.

  • $\begingroup$ Thanks, what does the question mean about "inner part of A" and "outer part of B" though? $\endgroup$
    – nzkiwi888
    Commented Dec 13, 2017 at 22:28
  • $\begingroup$ It just means that one magnet is on the inner side of the "building" and the other on the inside. It's very badly writen. Don't concern yourself with such things and rather find a better learning book. :) $\endgroup$
    – MaDrung
    Commented Dec 14, 2017 at 7:30

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