Q. A particle covers half of its total distance with speed v₁ and the rest half distance with speed v₂. Its average speed during the complete journey is
A) v₁²v₂²/(v₁² + v₂²)
B) (v₁ + v₂)/2
C) v₁v₂/(v₁ + v₂)
D) 2v₁v₂/(v₁ + v₂)
Explanation
[Solution from source] Each half takes d/v₁ and d/v₂, so average speed = 2d/(d/v₁ + d/v₂) = 2v₁v₂/(v₁ + v₂), the harmonic mean. The arithmetic mean (v₁ + v₂)/2 would apply only to equal time intervals, not equal distances. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.