InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
3. Between two stations a train accelerates uniformiy at first, then moves with constant speei and finalyretards uniformly to come to rest. If the catics of time taken are 1 8 1 and the greatest speedis 60 km/hour. Then the average speed over the whole journey(1) 45 km/hr(2) 54 km/hr(3) 35 kmlhr(4) 53 km/hr |
|
Answer» Let it accelerates with say ‘a’ in time ‘x’ then it reaches a velocity ‘v’ and continues motion for time ‘8x’ abd finally then retards with ‘b’ in time ‘x’. v = 0 + ax => v = ax => 60 = ax => a = 60/x And, 0 = v – bx => b = 60/x Distance covered in time of acceleration, S1= 0 + ½ at2 => S1= ½ ax2= ½ × 60/x × x2= 30x Distance covered while moving with constant velocity is, S2= vt = 60 × 8x = 480x Distance covered in time of retardation, 02= v2- 2bS3 => S3= 602/(2 × 60/x) => S3= 30x So, total distance = 30x + 480x + 30x = 540x Total time = x + 8x + x = 10x average velocity = 540x/10x = 54 km/h very complicated method |
|