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    Question taken from:

    https://isaacphysics.org/questions/c...lls_book_ch_h2

    Two charges are stuck to a metre stick: a +1.0pC charge at the 0cm mark,
    and a −1.0pC charge at the 10cm mark.
    What is the strength of the electric field at the 20cm mark?

    Am I correct in assuming that 20cm mark the field strength is due only to the -1pC point charge giving a value of 0.9N/C ( i.e. 9x10^9x1x10^-12/0.01^2)?
    The application on the web page refuses to accept that as the right value.
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    (Original post by xlaser31)
    Question taken from:

    https://isaacphysics.org/questions/c...lls_book_ch_h2

    Two charges are stuck to a metre stick: a +1.0pC charge at the 0cm mark,
    and a −1.0pC charge at the 10cm mark.
    What is the strength of the electric field at the 20cm mark?

    Am I correct in assuming that 20cm mark the field strength is due only to the -1pC point charge giving a value of 0.9N/C ( i.e. 9x10^9x1x10^-12/0.01^2)?
    The application on the web page refuses to accept that as the right value.
    Work out the field strength at 20cm due to each charge in turn and then add together...
    the fancy name for this is superposition
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    (Original post by xlaser31)
    Question taken from:

    https://isaacphysics.org/questions/c...lls_book_ch_h2

    Two charges are stuck to a metre stick: a +1.0pC charge at the 0cm mark,
    and a −1.0pC charge at the 10cm mark.
    What is the strength of the electric field at the 20cm mark?

    Am I correct in assuming that 20cm mark the field strength is due only to the -1pC point charge giving a value of 0.9N/C ( i.e. 9x10^9x1x10^-12/0.01^2)?
    The application on the web page refuses to accept that as the right value.
    Both charges will have effect on the field strength at 20 cm. -1.0pC will cause attraction and +1.0pC will cause repulsion if there is a positive point charge at 20 cm. To add on, your conversion from cm to m is incorrect.
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    I hope i am right
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