力學難題!!!!!!!!!!!!

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3 Answers

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  • 1 decade ago
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    It should be B, (1) and (2)

    (1), Work done = Fs

    = area under the graph

    = xy /2 J

    So, (1) is correct.

    (2). By Newton's 2nd law of motion

    F = ma

    From the graph, F is +ve throughout the journey, so acceleration is positive also.

    When acceleration is positive, velocity increases.

    So, the velocity increases for the whole journey and statement (2) is correct.

    (3) As mentioned in (1), area of the graph is work done, not distance.

    Distance is presented in the x-axis.

    So, this statement is wrong.

    Source(s): Myself~~~
  • 1 decade ago

    good.

    簡而清.

  • 1 decade ago

    B

    1is correct, workdone = Fs

    the area bounded with the x axis by the line

    xy/2 = workdone

    2 is correct, it accelerate in the first part

    but the force decreasing that means

    F (下降緊) = m (constant) a (下降緊)

    force 跟 acceleration 是 正比,

    雖然acceleration 下降緊, 但都係有acceleration

    而a 依然係postive, thats mean velocity is still increasing in 下半部份

    3 is wrong, because 1 is correct

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