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Equipotential-Edexcel watch

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    Now, i'm totally confused on this. What is the value of the equipotential lines as they get further away from the centre of the earth? Do they get smaller, or do they increase? In the edexcel text book, it shows that the equipotential lines' values INCREASE as they get further away from the earth's surface. However, in one of the tests that i sat, the answer was the value decreases as it gets further away from the earth. Now, who's right? I also realised that the values given in both questions aren't the same, in the text book, the values are positive whereas in the test, the values were negative. Both of them have the same units.By my own reasoning, i think the values should decrease as the lines show the gravitational field strength at that particular distance from the earth and it's kind of a common sense that the further away that point is, the weaker the gravitational field strength and hence smaller value.

    Please enlighten me on this matter. Thanks in advance.
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    We know that F = -1/r^2 (times some constant, i.e. -GmM/r^2, which I won't bother to write in from now on), and it's often taken that V = -\int F\text{ d} r, which makes V = -1/r. So as r increases, V increases towards 0. On the other hand, this is purely convention; getting rid of the minus sign would make no difference as long as you did so consistently.
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    So, should the value increase or decrease as the equipotential lines get further away from the earth? The text book says it will increase while the test paper says it will be of the opposite.
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    (Original post by ~Adel~)
    So, should the value increase or decrease as the equipotential lines get further away from the earth? The text book says it will increase while the test paper says it will be of the opposite.
    Defining the zero of potential to be at infinity, the value increases as you move away from the object, however it's magnitude decreases.
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    Aren't ''values'' and ''magnitude'' the same thing?
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    (Original post by ~Adel~)
    Aren't ''values'' and ''magnitude'' the same thing?
    No, a value can be positive or negative, a magnitude is positive. For example, 1 and -1 both have a magnitude of 1, but they are not the same value.
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    Yeah..so..urm..i don't seem to get the answer for my question, yet.(forgive me if i'm slow). Now, i need a straight forward answer. Does the magnitude gets bigger OR smaller as it goes further away from the earth?
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    I don't really understand the question but I will try to answer. Because gravitational strength varies according to the inverse square rule, its magnitude should reduce the further it is. However the distance between one equipotential line to the next will increase.
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    So, let's say you are asked to label three equipotential lines around the earth. You are given three values, -56Mj/kg, -46Mj/kg and -36Mj/kg. What is the value that you'll use to label the equipotential line which is furthest from the earth.
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    -36
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    The second part of the question: Explain the values that you've used.

    have a look at the edexcel text book, page 17 and please kindly tell me why is the text book saying otherwise.
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    The value increases.
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    Why is it so? Now, who's right? Sphixter or Robob? The answers in the tests say the magnitude will decrease as it gets further away though.
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    It does and has. We're both saying the same thing. -36 is smaller than -56. The sign just shows direction.
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    I think not to confuse anyone you mean't -36 is greater than -56, so it is increasing. I think i understand what you are confused about.

    The answer in the paper did actually increase , but because it showed a negative sign it tricked you. If you think about it logically, -56 actually less than -36, and -36 is actually greater than -56. Numbers increase as they go from -56 to 0 but numbers will decrease if they went from +56 to 0. I hope that helped, I do a level maths but still sometimes forget the basics of this.
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    I think this is a vector quantity. So the sign doesn't really matter. The magnitude will DECREASE as the distance INCREASES. The sign is only there to show the intended direction which is towards the mass.
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    OK, i think i'll just stick to what sphixter said as that's what i thought initially.
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    It isn't a vector quantity, just a scalar that can be positive or negative.

    As you move further away the value increases (i.e. from -56 to -36 ).
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    (Original post by sphixter)
    It does and has. We're both saying the same thing. -36 is smaller than -56. The sign just shows direction.
    An energy doesn't have a direction.
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    OP, are you talking about gravitational field strength or energy? If you're talking about field strength then it is a force and so can have direction. If it is energy then disregard what I said above.
 
 
 
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