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A train travelling at 20km/hr is approaching a platform .A bird is sitting on a pole on the pole on the platform.When the train is at a distance of 2km from pole,brakes are applied which which produce a uniform deceleration in it.At instant the bird flies towards the train at 60km/hr and after touching the nearest pt on the train flies back to the pole and then flies towards the train and continues repeating itself.Calculate how much distance will the bird have flown before the train stops?e is approachi

Asked by m.nilu 20th July 2018, 9:49 PM
Answered by Expert
Step 1 : Fnding the acceleration of the train when it is at the distance of 2 km from the pole.
begin mathsize 12px style straight v squared space equals space straight u squared plus 2 as
end style
final velocity 'v' is 0 because it is assumed that the train is supposed to stop when it reaches the pole.
initial velocity = 20 km/hr ...(given)
s = 2 km, the distance of the train from the pole.
begin mathsize 12px style straight v squared space equals space straight u squared plus 2 as
0 equals space 20 squared plus 2 straight a left parenthesis 2 right parenthesis
straight a equals fraction numerator negative 400 space over denominator 4 end fraction
straight a equals space minus 100 space km divided by hr squared
end style
Step 2: Finding the time in which the train travelled 2kms to the pole.
begin mathsize 12px style straight v space equals space straight u plus at
0 equals 20 space plus space left parenthesis negative 100 right parenthesis straight t
straight t equals fraction numerator negative 20 over denominator negative 100 end fraction equals 1 fifth space hr end style
Step 3: Finding the distance that the bird covers in the above period of time.
distance = speed (of bird) x time (above calculated)
begin mathsize 12px style distance space equals space 60 space straight x space 1 fifth
distance space equals space 12 space km end style
Answered by Expert 26th July 2018, 12:37 PM
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