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M1 Impulse question

A ball of mass 0.2kg falls vertically and strikes horizontal ground with a speed of 8m/s. The ball rebounds vertically with a speed of 6m/s.
Find the impulse exerted on the ball by the ground during the impact.

I got 28Ns but the mark scheme had -28Ns. Why do they take -6 and then positive 8 when working out I instead of -8 and 6?
Original post by ozmo19
A ball of mass 0.2kg falls vertically and strikes horizontal ground with a speed of 8m/s. The ball rebounds vertically with a speed of 6m/s.
Find the impulse exerted on the ball by the ground during the impact.

I got 28Ns but the mark scheme had -28Ns. Why do they take -6 and then positive 8 when working out I instead of -8 and 6?


Where is this from? Edexcel questions would always ask for the magnitude of the impulse since it is entirely up to you whether you take up or down as positive. If it wants the direction as well, then it would be upwards, rather than a + or - issue.
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ozmo19
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Original post by tiny hobbit
Where is this from? Edexcel questions would always ask for the magnitude of the impulse since it is entirely up to you whether you take up or down as positive. If it wants the direction as well, then it would be upwards, rather than a + or - issue.


This is from a CCEA M1 paper.
Ok, thanks

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