2025 · Q2
A car travels a total distance L. It travels half the distance with speed v1 and the other half with speed v2. The average speed of the car is:
General KnowledgePhysics
- A(v1 + v2)/2
- B2v1v2/(v1 + v2)
- C(v1 + v2)L/2v1v2
- D0
Explanation
Average speed equals total distance divided by total time. Each half of distance L takes time (L/2)/v1 and (L/2)/v2 respectively, so total time is (L/2)(1/v1 + 1/v2) = L(v1+v2)/(2v1v2). Dividing L by this gives 2v1v2/(v1+v2), which is the harmonic mean of the two speeds. The arithmetic mean (v1+v2)/2 would apply only if the car travelled for equal times at each speed, not equal distances, so option A is a distractor.