Question

a train covers half of its journey with a speed of 30 metre per second and the other half the speed of 40 metre per second calculate the average speed of train during then whole journey​

Answer 1

Answer:

let total distance = x

time1 = x/30

time2= x/40

total time = 7x/120

avg speed = total distance / total tym

= (x/7x )×120 = 17.14 m/s

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Answer 2

Explanation:

Let the distance covered by train = 2x m

Case 1:

Speed = 30 m/s

Time Taken = (x m)/(30 m/s) = x/30 s

Case 2:

Speed = 40 m/s

Time Taken = (x m)/(40 m/s) = x/40 s

So, Average Speed = Total Distance Covered / Total Time Taken

$= \frac{2x}{ \frac{x}{40} + \frac{x}{30} } \\ \\ = \frac{2x}{ \frac{3x + 4x}{120} } \\ \\ = \frac{2x}{ \frac{7x}{120} } \\ \\ = \frac{240x}{7} = 34.28 \: m {s}^{ - } \: approximately$