Hooke's Law Mark Scheme - can you explain this?

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vector12
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The first line of the mark scheme says plastic, but then it suggests that you'd get marks for stating any of them and explaining it? Is that right?

If you'd only get marks for saying plastic, why would it be more likely to demonstrate plastic behaviour rather than tough behaviour? Surely it would need to be both tough and elastic and plastic? Which would be most likely and why?
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uberteknik
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(Original post by vector12)

The first line of the mark scheme says plastic, but then it suggests that you'd get marks for stating any of them and explaining it? Is that right?

If you'd only get marks for saying plastic, why would it be more likely to demonstrate plastic behaviour rather than tough behaviour? Surely it would need to be both tough and elastic and plastic? Which would be most likely and why?
For part i). two marks are awarded for the correct answer and an appropriate description. One mark is awarded for an incorrect choice as long as it is accompanied by a correct description for that choice.

The second paragraph of the question states that "Hard body armour gives more protection but is heavier and does not give any flexibility of movement.

That rules out ductile and elastic.

The properties for the body armour need to be strong and tough but also balanced with weight. i.e. medium density. Comparing materials for strength and toughness, polymers (generic plastic) are the closest match. e.g. polycarbonate, nylon etc. An even better choice are composite materials.

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vector12
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(Original post by uberteknik)
For part i). two marks are awarded for the correct answer and an appropriate description. One mark is awarded for an incorrect choice as long as it is accompanied by a correct description for that choice.

The second paragraph of the question states that "Hard body armour gives more protection but is heavier and does not give any flexibility of movement.

That rules out ductile and elastic.

The properties for the body armour need to be strong and tough but also balanced with weight. i.e. medium density. Comparing materials for strength and toughness, polymers (generic plastic) are the closest match. e.g. polycarbonate, nylon etc. An even better choice are composite materials.

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So you could have said tough or plastic and defined it? Is that right?
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uberteknik
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(Original post by vector12)
So you could have said tough or plastic and defined it? Is that right?
The answer required plastic with a correct definition for full marks.

Tough with a definition would give 1 mark.
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(Original post by uberteknik)
The answer required plastic with a correct definition for full marks.

Tough with a definition would give 1 mark.
Thank you. Why would the answer require plastic and not tough?
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(Original post by vector12)
Thank you. Why would the answer require plastic and not tough?
I suggest It comes down to the choice of material including weight and flexibility of movement as defined by the question.

It's a bit ambiguous I agree, as plastic describes both the material properties and the material composition. My reading is that the mark scheme inadvertently requires both to be considered.

Tough materials can range from rubbers to metals to plastics. I.e. tough does not tie down the requirements for the body armour to be light as well. Some exam questions can be ambiguous at the best of times.
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