1.

A vehicle travels half the distance (L) with speed ` V_1` and the other half with speed ` V_2`, then its average speed is .A. `v_1 + v_2/2`B. `2v_1 + v_2/v_1 + v_2`C. `2v_(1)v_2/v_1 + v_2`D. `L(v_1 + v_2)/v_(1)v_(2)`

Answer» Correct Answer - (c )
Time taken to travel first half distance,
`t_1 = (L/2)/v_1 = L/(2v_1)`
Time taken to travel second half distance, `t_2 = (L/2)/v_2 = L/(2v_2)`
Total time taken = `t_1 + t_2 = L/(2v_1) + L/(2v_2)`
Average speed `= ("Total distance travelled")/("Total time taken")`
`= L/(L/(2v_1) + L/(2v_2)) = 1/(1/2[1/v_1 + 1/v_2]) = (2v_(1)v_(2))/(v_(2) + v_(1))`


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