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    (Original post by metrize)
    Is impulse always in the direction yhe particle moves after the collision? Also wjats thrust in a tow bar
    thrust is basically the opposite of tension.

    Imagine tension happens when you stretch a string, thrust occurs when you compress a string.

    Generaly Impulse acts opposite to the particle so for example:


    O----> <-Impulse-> <----O
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    (Original post by metrize)
    Is impulse always in the direction yhe particle moves after the collision? Also wjats thrust in a tow bar
    Impulse is always in the opposite direction....because its the change of momentum. So the momentum will have changed negatively as a collision sends it the other way....which is why particle A's is always negative and B's is always positive as we take the direction if A as positvie
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    Scale of 1 to 10 how scared is everyone for this exam (10 being a horror film in real life).
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    (Original post by IAROX15)
    Scale of 1 to 10 how scared is everyone for this exam (10 being a horror film in real life).
    5/6
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    (Original post by IAROX15)
    Scale of 1 to 10 how scared is everyone for this exam (10 being a horror film in real life).
    It is a tough one, im getting 70/75 for core 3 and 4 gold exams but for some inexplicable reason i cant not make really dumb errors on mechanics papers...its infuriating.

    Its definately the paper that is easiest to mess up on
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    (Original post by KloppOClock)
    thrust is basically the opposite of tension.

    Imagine tension happens when you stretch a string, thrust occurs when you compress a string.

    Generaly Impulse acts opposite to the particle so for example:


    O----> <-Impulse-> <----O

    So if object A and B connected via towbar which has a thrust, woukd it be like this

    A--<->--B
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    (Original post by philo-jitsu)
    It is a tough one, im getting 70/75 for core 3 and 4 gold exams but for some inexplicable reason i cant not make really dumb errors on mechanics papers...its infuriating.

    Its definately the paper that is easiest to mess up on
    I read an examiners report and they penalise you for answers which are 'too precise'??!?
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    (Original post by metrize)
    So if object A and B connected via towbar which has a thrust, woukd it be like this

    A--<->--B
    Yes, but you have to know when that thrust would occur. For example, say if B was a car and A was a trailer, if B moving at speed then decided to brake, thrust would occur as the towbar would compress.
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    (Original post by IAROX15)
    I read an examiners report and they penalise you for answers which are 'too precise'??!?
    whenever you use an aproxomations such as g=9.8 you have to round to 2 or 3 significant figures.
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    (Original post by IAROX15)
    I read an examiners report and they penalise you for answers which are 'too precise'??!?
    Really!?...well thats comforting....i always use 9.81 for gravity because thats what we use for ohysics....defo could lose some points for that
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    (Original post by philo-jitsu)
    Really!?...well thats comforting....i always use 9.81 for gravity because thats what we use for ohysics....defo could lose some points for that
    oh gosh i really hope that doesnt trip me up.
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    (Original post by Cryptokyo)
    In regards to your questions.



    1. The question states that u^{2}&lt;\frac{1}{2}gl. This inequality is here such that the particle with speed 2u does not collide with the pulley. Hence neither particle goes above a height l from their original position.



    2. Both particles must get tension at the same time as they are connected by a single string. Tension occurs will the length of the string is of definite length 2l with no slack. In reality there would be rebound but this does not have to be considered for the question.



    3. There would be tension if, and only if both particles were in their original position.

    Hints for question
    Split the problem into the 3 parts:
    - When both A and B are going upwards.
    - When A is going upwards and B goes downwards.
    - When both A and B are going downwards.

    Hope this helps,
    Cryptokyo
    Do you think something like this could come up in the real exam?
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    (Original post by RKM21)
    Do you think something like this could come up in the real exam?
    100% No. A question like that has never come up before.
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    (Original post by Pavinder100)
    The likelihood of this happening is slim, but what would you lot do if there was a question about pulleys where instead of it being smooth it was rough
    Question 8 from june 2015 IAL has a pully with a rough surface. Try it its easier than you think!
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    (Original post by KloppOClock)
    Yes, but you have to know when that thrust would occur. For example, say if B was a car and A was a trailer, if B moving at speed then decided to brake, thrust would occur as the towbar would compress.
    Ah that makes sense, thanks a lot!
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    (Original post by rockingmax)
    Question 8 from june 2015 IAL has a pully with a rough surface. Try it its easier than you think!
    Im assuming you just apply friction the opposite direction of the heaviest object?...beauce friction would be opposing the acceleration?
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    (Original post by rockingmax)
    Question 8 from june 2015 IAL has a pully with a rough surface. Try it its easier than you think!
    I looked at that question , its a smooth pulley
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    (Original post by rockingmax)
    Question 8 from june 2015 IAL has a pully with a rough surface. Try it its easier than you think!
    i think he means the actualy pulley being rough
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    Could someone help me with January 2014 IAL Q7b :/
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    (Original post by RKM21)
    Do you think something like this could come up in the real exam?
    No. It is a bit too much for a single question and normally it would have numbers rather than letters. But of course pulleys will be tested in the exam, but this question goes a bit further than needs be for the topic of pulleys.
 
 
 
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