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    For question 7 of the June 2011 edexcel paper, is the reaction force at A at an angle or perpendicular? I initially thought it would be perpendicular as the question does not say the rod is hinged to the wall, but the rod is against the wall. However the exam solutions video says it is at an angle. Can someone please clarify this?

    Thanks!
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    (Original post by Glavien)
    For question 7 of the June 2011 edexcel paper, is the reaction force at A at an angle or perpendicular? I initially thought it would be perpendicular as the question does not say the rod is hinged to the wall, but the rod is against the wall. However the exam solutions video says it is at an angle. Can someone please clarify this?

    Thanks!
    The wall is rough so there is a frictional force upwards as well as the normal reaction acting perpendiculr to the wall, i.e. along the rod.

    You could put these together as a force at an angle, but I think it's better to keep them separate.

    Part b is asking just for the magnitude of the normal reaction. In part c you need to use F = mu R.
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    (Original post by tiny hobbit)
    The wall is rough so there is a frictional force upwards as well as the normal reaction acting perpendiculr to the wall, i.e. along the rod.

    You could put these together as a force at an angle, but I think it's better to keep them separate.

    Part b is asking just for the magnitude of the normal reaction. In part c you need to use F = mu R.
    Yes thank you, I think I got it. Just to clarify this diagram is correct right?

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    (Original post by Glavien)
    Yes thank you, I think I got it. Just to clarify this diagram is correct right?

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    Yes.
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    For question 3(b) of the January 2012 M2 paper, why when you work out the work done, you only use the constant resistance force of 20N? Surely, there is also work done against the component of the weight acting down the plane, right?

    Paper: https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf
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    (Original post by Glavien)
    For question 3(b) of the January 2012 M2 paper, why when you work out the work done, you only use the constant resistance force of 20N? Surely, there is also work done against the component of the weight acting down the plane, right?

    Paper: https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf
    Sure, work done against gravity/weight is called G.P.E and I presume you'e already including G.P.E in your calculations?
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    (Original post by Zacken)
    Sure, work done against gravity/weight is called G.P.E and I presume you'e already including G.P.E in your calculations?
    Yeah I did include G.P.E, that's why I got the answer correct while still being unsure. Thanks I get it now!
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    (Original post by Glavien)
    Yeah I did include G.P.E, that's why I got the answer correct while still being unsure. Thanks I get it now!
    It's a very common question.
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    Does the coefficient of friction have range of 0<u<1 or 0<=u<=1 ?
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    (Original post by Glavien)
    Does the coefficient of friction have range of 0<u<1 or 0<=u<=1 ?
    It can be greater than 1, e.g. aluminium on aluminium is 1.4.

    When a surface is modelled as "smooth", we are effectively taking mu as 0.
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    (Original post by tiny hobbit)
    It can be greater than 1, e.g. aluminium on aluminium is 1.4.

    When a surface is modelled as "smooth", we are effectively taking mu as 0.
    Ohhh, never knew that. Thanks.
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    (Original post by Glavien)
    Ohhh, never knew that. Thanks.
    So, if a question asks you to find the range of mu and lets say you got mu<0.5 . Should you just leave it as mu<0.5 or 0<mu<0.5 ?
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    The question says 'the strut is freely hinged to the rod at point D'. Does that mean there is thrust acting on the rod as well as a reaction force from the strut on the rod? Or is the reaction force the thrust?

    Also, if it did not say 'hinged' but it said the rod rested on the strut at D would this a difference to the forces at D?Name:  ImageUploadedByStudent Room1465779336.377912.jpg
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    (Original post by Glavien)
    The question says 'the strut is freely hinged to the rod at point D'. Does that mean there is thrust acting on the rod as well as a reaction force from the strut on the rod? Or is the reaction force the thrust?

    Also, if it did not say 'hinged' but it said the rod rested on the strut at D would this a difference to the forces at D?Name:  ImageUploadedByStudent Room1465779336.377912.jpg
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    hinges give reactions in two directins so there inst only a reaction going perp to the wall like normal.
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    (Original post by physicsmaths)
    hinges give reactions in two directins so there inst only a reaction going perp to the wall like normal.
    Sorry, but not talking about the wall. I'm talking about the hinge at D. Would the reaction at that point be the thrust in the rod?


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    (Original post by Glavien)
    Does the coefficient of friction have range of 0<u<1 or 0<=u<=1 ?
    On the Jan 2012 3a question you did... Do you know why they rounded the power from 328.7N to 330N?
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    (Original post by fpmaniac)
    On the Jan 2012 3a question you did... Do you know why they rounded the power from 328.7N to 330N?
    I'm guessing because you have to give your answer to 3 or 2 sig figs.


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    Why can you not do this to find the value of k?

    Question 5 : https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf

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    (Original post by Glavien)
    Why can you not do this to find the value of k?

    Question 5 : https://ca99c64778b62ba7e7b339967029...%20Edexcel.pdf

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    You cannot multiply stuff like that. You have to equate coefficients. you have taken into account direction and it is dimensionally incorrect to square a vector leading to normal numbers.
 
 
 
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