physics

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(a) if a train travelling at 72km/hr is to be brought to rest in a distance of 200m then wat should be its retardation
(b) if a body starts from rest and and travels 120 m in 8th sec then wats its acceleration.

  • physics -

    (a) How do you define retardation?
    Is it deceleration?
    72 km/h = 20 m/s
    Average velocity during deceleration = 10 m/s.
    10*t = 200 m
    Deceleration time t = 20 s
    Deceleration rate = 20 m/s/20s
    = 1 m/s^2

    (b) If you are supposed to assume the acceleration rate is constant,
    X(8) - X(7) = (a/2)*(64-49)
    = 120
    15*(a/2) = 120
    a = 16 m/s^2

  • physics -

    A motor car moving with a velocity of 54km/hr is brought to rest in (i) 5sec (ii) 3meter. Find the retardation in each case.

  • physics -

    10*t = 200 m


    this is wrong ????? because velocity is 20m/s

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