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OCR Gateway Physics B - P4 P5 P6 - Unofficial Mark Scheme watch

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    (Original post by Arian Nazifi)
    Calculations of the top of my head

    p5

    Resultant velocity would be 6 so Y is greatest

    Would take horse 7 seconds

    Car wasn't over speed limmit, it was 6.5 m/s

    P5 6 maker: 0.45
    Resultant velocity was 6 for X not Y I think.

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    (Original post by some-student)
    I think it was that when it gets dark the LDR gets a higher resistance and so has a higher share of the output voltage and when it gets really dark the LDR will have such a high resistance that the output voltage is basically the input voltage which is 5V - a logical 1 and so turns on the light



    It was NOR
    But it did not have that curvy shape of the OR gate...
    So my answer for the six mark question is incorrect?
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    (Original post by mxskaan)
    Resultant velocity was 6 for X not Y I think.

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    I put X too...
    It was 3 in one direction and 3 in another, so is it correct to add the two opposite velocities?
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    (Original post by Wolfram Alpha)
    I put X too...
    It was 3 in one direction and 3 in another, so is it correct to add the two opposite velocities?
    No, you subtract the velocities if they're in opposite directions
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    (Original post by Wolfram Alpha)
    I put X too...
    It was 3 in one direction and 3 in another, so is it correct to add the two opposite velocities?
    I thought it was subtract....

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    (Original post by Wolfram Alpha)
    But it did not have that curvy shape of the OR gate...
    So my answer for the six mark question is incorrect?
    I'm not sure about your answer to the six mark - it depends on what the examiner thinks

    And about the logic gates, there was a NOT gate, and AND gate, and a NOR gate.
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    (Original post by leopard923)
    I thought it was subtract....

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    I realised after the exam. I did terribly.
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    Just thought that I'd make some predictions regarding the grade boundaries. Feel free to leave feedback.

    Predicted grade boundaries P4 P5 P6 [HIGHER] 2016
    The previous grade boundaries were as follows;
    2015- A*: 54, A: 45, B: 36, C: 27
    2014- A*: 57, A: 48, B: 39, C: 30
    2013- A*: 52, A: 43, B: 34, C: 25
    Personally, while the calculations were rather difficult and some of the questions were phrased oddly, the majority of the questions were accessible to a large group of people. My predictions for the grade boundaries are; A*: 55, A: 46, B: 36, C: 29.
    Hope this helps!
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    (Original post by GCShElpme)
    I thought it was an OR gate.
    It was NOR as it had that circle after it.
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    (Original post by Wolfram Alpha)
    I realised after the exam. I did terribly.
    I'm sure you didn't! From the other science threads you seen really clever anyways

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    (Original post by GCShElpme)
    Just thought that I'd make some predictions regarding the grade boundaries. Feel free to leave feedback.

    Predicted grade boundaries P4 P5 P6 [HIGHER] 2016
    The previous grade boundaries were as follows;
    2015- A*: 54, A: 45, B: 36, C: 27
    2014- A*: 57, A: 48, B: 39, C: 30
    2013- A*: 52, A: 43, B: 34, C: 25
    Personally, while the calculations were rather difficult and some of the questions were phrased oddly, the majority of the questions were accessible to a large group of people. My predictions for the grade boundaries are; A*: 55, A: 46, B: 36, C: 29.
    Hope this helps!
    I agree

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    The resistance in an LDR decreases as light intensifies and increases if light intensity decreases.
    If resistor 1 has a higher resistance than resistor 2 (LDR), the voltage is taken through the first output. This means the security light will stay off.
    If resistor 2 (LDR) has a higher resistance than resistor 1 the voltage will go through that and out the bottom output, powering the security light.
    I'm not too sure if this is correct but it's what i put.
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    (Original post by leopard923)
    I thought it was subtract....

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    It was Y as x had the resultant force of 0 but y was 6 as if it goes in same direction you add for forces.
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    (Original post by NothingButJames)
    The resistance in an LDR decreases as light intensifies and increases if light intensity decreases.
    If resistor 1 has a higher resistance than resistor 2 (LDR), the voltage is taken through the first output. This means the security light will stay off.
    If resistor 2 (LDR) has a higher resistance than resistor 1 the voltage will go through that and out the bottom output, powering the security light.
    I'm not too sure if this is correct but it's what i put.
    I said very similar

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    (Original post by mxskaan)
    You do add dw. For resultant velocity you add and for resultant FORCE you subtract. The question clearly stated velocity.

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    I did research and you are absolutely correct. Thanks for that, it's reassuring .
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    (Original post by NothingButJames)
    The resistance in an LDR decreases as light intensifies and increases if light intensity decreases.
    If resistor 1 has a higher resistance than resistor 2 (LDR), the voltage is taken through the first output. This means the security light will stay off.
    If resistor 2 (LDR) has a higher resistance than resistor 1 the voltage will go through that and out the bottom output, powering the security light.
    I'm not too sure if this is correct but it's what i put.
    I'm not too sure, but I think regardless of the resistance of either, the voltage comes out of the same place:
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    (Original post by leopard923)
    I'm sure you didn't! From the other science threads you seen really clever anyways

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    Your comment made me laugh and thank you. I'll just hope my examiner is half asleep so I get extra marks AND my exam is not remarked by someone else. And the probably of this happening is...well, let's not go there.
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    (Original post by Wolfram Alpha)
    I did research and you are absolutely correct. Thanks for that, it's reassuring .
    I was beginning to doubt myself, thank you so much for researching!
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    (Original post by some-student)
    OCR Gateway Physics B
    P4 P5 P6 + Section D
    Unofficial Mark Scheme
    Wednesday 22 June 2016

    Module P4 - 25 marks
    1) Radiation treatment
    a) Explain why an alpha source cannot be used as a tracer [1]
    (too ionising and so) will not penetrate out of the skin (1)

    b)i) Explain why a radioactive source should not remain in the body for a long time [1]
    to not cause damage to healthy living cells (1)

    b)ii) What is the name given to how long a source stays radioactive? [1]
    half-life / radioactivity (1) not sure [I believe I wrote half-life.]

    c) Radiation may be used to treat brain cancer - explain why the head should be clamped [2]
    so that the gamma rays are focused on the tumour (1)
    to avoid damage to non-cancerous / healthy tissue / cells (1)

    2) Fuses and wiring [6]
    Marking points
    why only two wires are needed: it is double insulated and so the earth wire is not needed - even if the live wire becomes loose, the plastic cannot become live: maybe include purpose of live and neutral wires (to carry the voltage and complete the circuit respectively)

    why a fuse is needed: too large a current causes the fuse to melt, preventing flow of current, which prevents flex overheating and causing fire - and prevents further damage to appliance

    why a 13A fuse is used instead of 3A: operating current must be between 3A and 13A so that the fuse does not break under normal operation (this would happen for a 3A fuse), but also breaks if the current gets too high

    3) Static electricity
    a) Complete the sentence [1]
    he gains a positive charge because he loses electrons (1)

    b) Explain how anti-static sprays work [1]
    make surface of object conductive (1)

    c) Explain why the small strip attached to his car may be unreliable [1]
    not touching the ground / not made of a conductor (1) not sure [Because it was a small strip attached to the back of the car, I wrote something referring to the fact that it may be unsupported/weak/easy to break off.]

    d) Describe and risk and benefit of the petrol filler [2]
    risk: spark due to static charges which could cause an explosion (1)

    benefit: quick to use as flows out quickly [This would be a benefit, as it reduces the time in which the pump and the car are in contact, thus reducing the risk of explosions.] / does not build up as much charge as it flows out quickly (1) not sure

    4) Nuclear radiation
    a) Write the letters in order [2]
    B, E, F, A

    four correct (2)
    two or three correct (1)
    otherwise (0)

    b) Explain the purpose of boron rods but explain why they need to be removed some times [2]
    absorb excess electrons to stop reaction going out of control (1)

    (need to be removed so that) there are enough neutrons for the reaction to continue (1)

    5) Power, current, resistance and voltage
    a) Calculate the output voltage of the adapter [2]
    94V (2)
    incorrect answer with workings (1)

    b) In which country will the iron have the highest electrical power? They all use the same current. Explain your answer [1]
    Kenya, because it has the highest input voltage (1)

    c) In Japan, the iron is bad at ironing out creases. She attaches a variable resistor and then it become better at ironing out creases. Explain why [2]
    before, it had a low power as they all used the same current and it had the lowest input voltage (1)
    variable resistor can be used to decrease resistance and increase current, making the power greater (1)
    Just thought I'd add a few things. Using this, I think I've managed to get 23-4 marks- that's a good start!
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    (Original post by Wolfram Alpha)
    Your comment made me laugh and thank you. I'll just hope my examiner is half asleep so I get extra marks AND my exam is not remarked by someone else. And the probably of this happening is...well, let's not go there.
    Loool you never know !

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