Physics, how to do(a), (b)?

Attachment image

1 個解答

評分
  • SC147
    Lv 6
    4 個月前
    最佳解答

    (a) In the 1st 5 sec, the car starts from 0 ms⁻¹, accelerating at 25/5 = 5 ms⁻², to 25 ms⁻¹

    It moves on at this constant velocity of 25 ms⁻¹ for 10 sec,

    Then, it decelerates at -25/(25-15) = -2.5 ms⁻², until it stops after another 10 sec.

    In the next 5 sec, it travels backwards*, accelerating at 20/5 = 4 ms⁻², to 20 ms⁻¹

    It moves on at this constant velocity of 20 ms⁻¹ for 5 sec,

    Finally, it decelerates at -20/(45-35) = -2 ms⁻², until it stops after 10 sec.

    (b) Total distance travelled

    = total area under the graph

    = ½ [(15-5)+25]x25 + ½ [(45-25)+5]x20

    = 437.5 + 50

    = 687.5 m

    * Explanation:-

    ==========

    The –ve sign of “velocity” indicates an OPPOSITE DIRECTION of the movement of the car, so that it is travelling backwards !

    • 登入以對解答發表意見
還有問題?馬上發問,尋求解答。