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Could someone help with this physics question please watch

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    A balls vertically in air from rest. The variation with time t for the distance d moved by the ball is
    shown.
    Referring to the graph, explain how it can be deduced that:
    i) the ball is initially at rest;
    ii) air resistance is not negligible.
    Using the graph:
    iii) determine the speed of the ball 0.40 s after it has been released.

    I'm completely lost I can't work out how I'm supposed to answer this any help would be much appreciated
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    Rephrasing the first two parts:

    (i) At rest means speed is zero, so how can you tell from the graph that the initial speed is zero? (What about a displacement time graph tells you the speed or velocity?)

    (ii) What part of the graph gives you the acceleration? If there were no air resistance, acceleration would be purely down to gravity, so would be a constant 9.81m/s2. How can you tell from the graph it's not constant?

    (iii) is the hardest for me - you need the speed AT THAT POINT rather than the average speed up to that point so it requires drawing a tangent to the line at the point where t = 0,4 s and finding the gradient of that line. It's the drawing the tangent I have difficulty with, I find it hard to judge by eye whether I've got it right. There are tricks you can use if you have mirror or tracing paper but since you won't have them in an exam it's probably best to try by eye.
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    (Original post by phys981)
    Rephrasing the first two parts:

    (i) At rest means speed is zero, so how can you tell from the graph that the initial speed is zero? (What about a displacement time graph tells you the speed or velocity?)

    (ii) What part of the graph gives you the acceleration? If there were no air resistance, acceleration would be purely down to gravity, so would be a constant 9.81m/s2. How can you tell from the graph it's not constant?

    (iii) is the hardest for me - you need the speed AT THAT POINT rather than the average speed up to that point so it requires drawing a tangent to the line at the point where t = 0,4 s and finding the gradient of that line. It's the drawing the tangent I have difficulty with, I find it hard to judge by eye whether I've got it right. There are tricks you can use if you have mirror or tracing paper but since you won't have them in an exam it's probably best to try by eye.
    Do you reckon they'd let you take in a mirror if it was your own and you explained why you wanted to use it? It doesn't specifically state anywhere that you can't use one. I remember for maths GCSE everyone was given a mirror
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    No, I'm pretty sure you can't.
    It might help while you're practising though, you could practise drawing the tangent and then use the mirror to check how close you are. Hopefully you'd get better with each attempt.
 
 
 
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