If a train travelling at 72 km h⁻¹ is brought to rest by applying brakes in a distance of 200 m, then the retardation of the train is
We use the kinematic equation:
v² = u² +2as
Substituting the values:
0 =(20)²+ 2a(200)
0 = 400 + 400a
400a = −400
a =−1 m/s²
The negative sign indicates retardation.
Thus, the retardation = 1 m/s².
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(d) Here initial velocity of train u = 72km/h = 72 5/18 m s⁻¹, final velocity of train v = 0 and distance covered by train during this time s = 200 m
∴ v² – u² = 2as
∴ (0)² – (20)² = 2(a) × 200 or -400 = 400 a ⇒ a = – 1 m s⁻²
Thus retardation of the train is 1 m s⁻².
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