Question

In a journey of 4 km a train travels with a constant acceleration for the first three-tenths of a km at a uniform speed of 30 km/hr for the next 3 km and with a constant retardation for the rest of the distance.
Find the time taken for the journey in minutes and the uniform retardation in m/s^2​

Answer 1

HI

v₁ = 20m/s t₁ = 10mins = 10 x 60  = 600 seconds = 1/6 hr s₁ = 12000 m = 12 km

s₂ = 8.5 km  t₂ = 10 mins = 600 seconds = 1/6 hr

s₃ = 11 km  t₃ = 10 mins = 1/6 hr

s₄ = 8.5 km  t₄ =  10 mins = 1/6 hr

s₅ = 6 km     t₅ = 10 mins = 1/6 hr

average speed =

total distance / total time = s₁ + s₂ + s₃ + s₄ + s₅ / t₁+ t₂+t₃+t₄+t₅  

12 + 8.5 + 11  + 8.5 + 6/ 1/6 + 1/6 +1/6 + 1/6 + 1/6= 46/(5/6) = 55.2 km/hr

Hope my answer is correct.

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