A car covers the first half of its journey at 60 km/h and the second half at 40 km/h. The AVERAGE speed for the whole journey is:
A48 km/h
B100 km/h
C50 km/h
D45 km/h
Answer & Solution
Correct answer: A. 48 km/h
Tricky: average speed ≠ simple average of two speeds when distances are equal. Use harmonic mean: avg = 2×60×40 / (60+40) = 4800/100 = 48 km/h. (Quick reason: more TIME is spent at the slower speed, so it pulls the average down.)
Related questions
In a velocity-time graph, the AREA UNDER the curve gives:In a distance-time graph, a STRAIGHT HORIZONTAL line means:A car braking uniformly decelerates from 20 m/s to rest with deceleration 5 m/s². The brakA train starts from rest (u = 0) and accelerates uniformly at a = 2 m/s² for t = 10 s. TheA car starting at u = 5 m/s accelerates uniformly at a = 2 m/s² for t = 4 s. Its final velA car accelerates from 10 m/s to 20 m/s in 5 seconds. Its acceleration is:A cab covers 60 km in 1.5 hours. Its AVERAGE SPEED is:A student runs once around a circular school playground of perimeter 400 metres and return