Hey there! Sign in to join this conversationNew here? Join for free
    Offline

    0
    ReputationRep:
    Can someone explain the moments question to me please?
    Offline

    0
    ReputationRep:
    I completely guessed 7a) F=2.5i and forgot to write j component. Showed hardly any working. How many marks could i get? I think it was out of 7 or 8 not sure.
    Offline

    2
    ReputationRep:
    Do units matter? If I forget to write the units for an answer e.g speed will I lose the mark?
    Offline

    2
    ReputationRep:
    (Original post by Ashelly)
    Can someone explain the moments question to me please?
    I can't remember the exact numbers.
    But...
    First you take moments about A when tilting about S. Tilting so reaction at T = 0.
    Then resolve forces vertically to find an equation for M.
    Rearrange for Reaction force at S and substitute into moments equation.

    Do the same but moments about B. Tilting about T so reaction at S = 0
    Resolve vertically for another equation for M.
    Rearrange for reaction force at T and substitute into moments equation.

    You now have two equations in terms of d and M... Solve simultaneously and voila.

    Maybe I did a long way - I can think of any shorter method though.
    Offline

    0
    ReputationRep:
    (Original post by JLegion)
    I can't remember the exact numbers.
    But...
    First you take moments about A when tilting about S. Tilting so reaction at T = 0.
    Then resolve forces vertically to find an equation for M.
    Rearrange for Reaction force at S and substitute into moments equation.

    Do the same but moments about B. Tilting about T so reaction at S = 0
    Resolve vertically for another equation for M.
    Rearrange for reaction force at T and substitute into moments equation.

    You now have two equations in terms of d and M... Solve simultaneously and voila.

    Maybe I did a long way - I can think of any shorter method though.
    I did it differently, what were your answers in the end?
    Offline

    0
    ReputationRep:
    Anyone know how many marks the moments question was worth?

    I took moments correctly around the left pivot but when it came to the left pivot I put the Durante as d-0.5 instead of 6-d. That mean both my answers for d and m were wrong

    Any idea how many marks I would have lost?
    Offline

    2
    ReputationRep:
    Guys for question 8.. I writ the equations right but after equating the a's I went wrong somewhere in my working out... I got 1.2N, but I realise now I've missed out g because 1.2g = 11.76 which is what the answer was... when equating the a's, g was in both equations I remember but I think I just forgot to times by g in the last step... how many marks do you think I will lose?

    Also, for 8b.. will I get method marks for using my value of the tension? I knew it would be 45 degrees to the horizontal so I put that.

    Any answers will be appreciated!!!
    Offline

    9
    ReputationRep:
    For question 7(a) I worked out F2 by drawing a scale diagram and still got 2.5i+2.5j

    Marks? I have a feeling the mark scheme will say "don't allow use of diagrams" or something like that.

    Also for the question with the pulley:

    One part of the question asked for the resultant force on the pulley from the string. Does this mean you did the route of (tension - friction)^2 + (weight - tension)^2?

    Is there an unofficial mark scheme anywhere?
    Offline

    1
    ReputationRep:
    (Original post by vvlp)
    For question 7(a) I worked out F2 by drawing a scale diagram and still got 2.5i+2.5j

    Marks? I have a feeling the mark scheme will say "don't allow use of diagrams" or something like that.
    I made a force triangle and solved it using the sine rule (and got the correct answer). I've seen mark schemes on similar questions and they allow you to solve like that as an alternative method.
    Offline

    1
    ReputationRep:
    Did anyone else get 1.6m and 66kg for the moments question? I went through it and checked it at the end but couldn't find any mistakes...
    Offline

    1
    ReputationRep:
    So I would have got full marks, but I scribbled out my correct answer to 2b (scale pan question) and included tension as a force, getting a new answer... (Don't ask me why! I know I'm a fool!) Do you think I will still get 1 mark for using F=ma and do you think 73 will be enough for 100UMS?
    Offline

    2
    ReputationRep:
    (Original post by aacargo)
    Did anyone else get 1.6m and 66kg for the moments question? I went through it and checked it at the end but couldn't find any mistakes...
    I got d=1.2 and M=42 which I have heard from a few people is the correct answer
    Offline

    3
    (Original post by TheFluffyCamel)
    So I would have got full marks, but I scribbled out my correct answer to 2b (scale pan question) and included tension as a force, getting a new answer... (Don't ask me why! I know I'm a fool!) Do you think I will still get 1 mark for using F=ma and do you think 73 will be enough for 100UMS?
    One of my teachers said if you crossed out the correct answer - provided that you didn't follow through with wrong answer - the examiners have to mark it(as long as they can read it).
    Offline

    2
    ReputationRep:
    (Original post by aacargo)
    Did anyone else get 1.6m and 66kg for the moments question? I went through it and checked it at the end but couldn't find any mistakes...
    I got that too.. but I think we went wrong by doing the distances wrong.. I think what I did was do the COM times the distance from A but it was supposed to be from the pivot!
    Not sure about you but I'm sure thats what i did wrong

    EDIT- just realised I did times by the right distances so not actually sure where I went wrong.. can someone explain?
    Offline

    9
    ReputationRep:
    (Original post by aacargo)
    Did anyone else get 1.6m and 66kg for the moments question? I went through it and checked it at the end but couldn't find any mistakes...
    d=1.2
    M=42
    Offline

    3
    (Original post by txnilxnur)
    I got that too.. but I think we went wrong by doing the distances wrong.. I think what I did was do the COM times the distance from A but it was supposed to be from the pivot!
    Not sure about you but I'm sure thats what i did wrong
    m=42 and d=1.2
    Offline

    2
    ReputationRep:
    (Original post by Ashelly)
    I did it differently, what were your answers in the end?
    d = 1.2 and M = 42, which seems to be the general consensus.

    How did you do it? Given my method took up 2 sides, I imagine yours was much quicker.
    Offline

    2
    ReputationRep:
    (Original post by Marxist)
    m=42 and d=1.2
    yes we know that
    Offline

    13
    ReputationRep:
    (Original post by TheFluffyCamel)
    So I would have got full marks, but I scribbled out my correct answer to 2b (scale pan question) and included tension as a force, getting a new answer... (Don't ask me why! I know I'm a fool!) Do you think I will still get 1 mark for using F=ma and do you think 73 will be enough for 100UMS?
    Literally me lol. Only marks and wrote it right but crossed out and changed my mind, the question was phrased really tricky.

    (Original post by SturtScooby)
    Could someone explain to me why the force exerted by the brick is 15.45N and not just its weight, 14.7N. I understand it's accelerating upwards and so there must be a net upwards force greater than the weight. The difference between the force and the weight is the force required to make it accelerate at 0.5m/s^2, so net upwards =1.5g + 0.5x1.5=15.45. Surely though, this is the force that the pan exerts on the brick and not what the brick exerts on the pan? Or am I correct and have I just messed up when reading the question and it's actually asked me to find the force of the pan on the brick
    Thought exactly the same thing matey. Wrote 14.7 after writing 15.5 just because of the phrasing.

    Posted from TSR Mobile
    Offline

    3
    ReputationRep:
    How many marks would I get for the following?

    7a) I used triangles and did it marginally wrong and got an answer of 5/root2 (i +j). I think one of my angles was incorrect. I put some notes down like F2 = x/root2 (i + j) and stuff. (worth 7 marks)

    3) The train question I stated the 2 equations

    40T + 40x/2 = 975
    30x25 + 30x/2 = 975

    Obviously x wasnt the same but I equated it and found a time for T.

    How manyh marks would I lose. (worth 8 marks)
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Brussels sprouts
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.