A car moves from `X` to `Y` with a uniform speed `v_u` and returns to `Y` with a uniform speed `v_d`. The average speed for this round trip is :A. `(2 v_d v_u)/(v_d + v_u)`B. `sqrt(v_u v_d)`C. `(v_d v_u)/(v_d + v_u)`D. `(v_u + v_d)/(2)`

A car moves from `X` to `Y` with a uniform speed `v_u` and returns to

1.	A car moves from `X` to `Y` with a uniform speed `v_u` and returns to `Y` with a uniform speed `v_d`. The average speed for this round trip is :A. `(2 v_d v_u)/(v_d + v_u)`B. `sqrt(v_u v_d)`C. `(v_d v_u)/(v_d + v_u)`D. `(v_u + v_d)/(2)`
Answer» Correct Answer - A We define Average speed `= ("Distance travelled")/("Time taken") = (d)/(T)` Let `t_1` and `t_2` be times taken by the car to go from `X` to `Y` and then from `Y` to `X` respectively. Then, `t_1 + t_2 =[(XY)/(v_u)]+[(XY)/(v_d)] = XY((v_u + v_d)/(v_u v_d))` Total distance travelled `d=XY+XY=2XY` Therefore, average speed of the car for this round trip is. `v_(av) = (2 XY)/(XY((v_u + v_d)/(v_u v_d)))` or `v_(av) = (2 v_uv_d)/(v_u + v_d)`.

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A car moves from `X` to `Y` with a uniform speed `v_u` and returns to `Y` with a uniform speed `v_d`. The average speed for this round trip is :A. `(2 v_d v_u)/(v_d + v_u)`B. `sqrt(v_u v_d)`C. `(v_d v_u)/(v_d + v_u)`D. `(v_u + v_d)/(2)`

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