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A person travelling in a straight line moves with a constant velocity v₁ for a certain distance x and with a constant velocity v₂ for the next equal distance. The average velocity v is given by the relation:

A

1/v = 1/v₁ + 1/v₂

B

2/v = 1/v₁ + 1/v₂

C

v/2 = (v₁ + v₂)/2

D

v = √v₁v₂

Step-by-Step Solution

  1. Definition of Average Velocity: Average velocity is defined as the total displacement divided by the total time interval . vavg=Total DisplacementTotal Timev_{avg} = \frac{\text{Total Displacement}}{\text{Total Time}}
  2. Calculate Time Intervals: For the first half distance xx, velocity is v1v_1. Time taken t1=xv1t_1 = \frac{x}{v_1}. For the second half distance xx, velocity is v2v_2. Time taken t2=xv2t_2 = \frac{x}{v_2}.
  3. Calculate Total Values: Total Displacement =x+x=2x= x + x = 2x. Total Time =t1+t2=xv1+xv2=x(1v1+1v2)= t_1 + t_2 = \frac{x}{v_1} + \frac{x}{v_2} = x \left( \frac{1}{v_1} + \frac{1}{v_2} \right).
  4. Derive Relation: v=2xx(1v1+1v2)v = \frac{2x}{x(\frac{1}{v_1} + \frac{1}{v_2})} v=21v1+1v2v = \frac{2}{\frac{1}{v_1} + \frac{1}{v_2}} Rearranging the terms: 1v=1v1+1v22\frac{1}{v} = \frac{\frac{1}{v_1} + \frac{1}{v_2}}{2} 2v=1v1+1v2\frac{2}{v} = \frac{1}{v_1} + \frac{1}{v_2}
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