Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 2)
2.
A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:
Answer: Option
Explanation:
| Speed of the train relative to man = |  |
125 |  m/sec |
| 10 |
| = | |
25 | m/sec. |
| 2 |
| = | |
25 | x | 18 | km/hr |
| 2 | 5 |
= 45 km/hr.
Let the speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr.
x - 5 = 45 
x = 50 km/hr.
Discussion:
475 comments Page 11 of 48.
Jeevitha said:
8 years ago
Somebody asking that why x-5 here. Note that the man running in the same direction. So we have to subtract. If it is opp we have to add. Because man beats train spd. So man power should be subtracted. Then only we can get an exact speed of the train.
Ramu nayak said:
7 years ago
Relative velocity is nothing but the velocity of body A to body B.
Case 1:
A and B moving in the same direction
Vr= Va-Vb. (Va>Vb)
Vr= Vb-Va (VB>Va)
Case 2:
A and B moving in opposite directions.
Vr=Va+VB. (Velocity not matters).
Case 1:
A and B moving in the same direction
Vr= Va-Vb. (Va>Vb)
Vr= Vb-Va (VB>Va)
Case 2:
A and B moving in opposite directions.
Vr=Va+VB. (Velocity not matters).
Saggy said:
9 years ago
Man is moving in same direction of train if man stop them train will less time to cross him but man is walking in same direction therefor man speed will be add in train speed if man walking in opposite direction of train then it minus from that.
Vishal Motwani said:
9 years ago
Important points to remember:
The Relative speed when two movable things whose speeds x, y are moving in the same direction is = x - y.
The Relative speed when two movable things whose speeds x, y are moving in OPPOSITE direction is =x + y.
The Relative speed when two movable things whose speeds x, y are moving in the same direction is = x - y.
The Relative speed when two movable things whose speeds x, y are moving in OPPOSITE direction is =x + y.
Malik said:
1 decade ago
@Preethi.
Relative speed u-v = 80-62= 18km/hr=(18* 5/18)= 5 m/s.
Total length a+b = 110+130= 240 m.
Time to overtake = (a+b)/(u-v)[see formula 9 from formula section]
= 240/5
= 48 sec.
Am I correct?
Relative speed u-v = 80-62= 18km/hr=(18* 5/18)= 5 m/s.
Total length a+b = 110+130= 240 m.
Time to overtake = (a+b)/(u-v)[see formula 9 from formula section]
= 240/5
= 48 sec.
Am I correct?
Keerthana P Tawade said:
2 years ago
T = L/V1-V2
Where
T = time taken by train to pass the pole
L = Length of the train.
V1 = velocity of the train.
V2= Velocity of the man.
10 = 125/V1-5kmph.
v1-5kmph = 125/10*18/5 (converting m/s into km/h).
V1-5kmph = 45kmph,
V1 = 50kmph.
Where
T = time taken by train to pass the pole
L = Length of the train.
V1 = velocity of the train.
V2= Velocity of the man.
10 = 125/V1-5kmph.
v1-5kmph = 125/10*18/5 (converting m/s into km/h).
V1-5kmph = 45kmph,
V1 = 50kmph.
(108)
Rohit said:
1 decade ago
Why is the distance covered by man in 10 sec not considered? I believe the total distance would be the length of train + distance covered by man in 10 sec. Considering this the relative speed of train comes out to 55 km/hr. Please suggest.
Mozammel hossain said:
6 years ago
There have man speed but not train speed.
So we known that;
speed = distanc/time.
= 125/10,
= 25/2.
Now convert into km/h.
25/2 * 18/5.
= 45km/h.
Lets train speed is x km/h.
So, the relative speed is x-5 km/h.
x- 5 = 45,
X = 50km/h.
So we known that;
speed = distanc/time.
= 125/10,
= 25/2.
Now convert into km/h.
25/2 * 18/5.
= 45km/h.
Lets train speed is x km/h.
So, the relative speed is x-5 km/h.
x- 5 = 45,
X = 50km/h.
PRIYANKA SHARMA said:
1 decade ago
Hello friends,
If you want to convert m/s into km/hr then multiply with 18/5.
For example: 5 m/s = 5m/s*18/5 = 18km/hr.
If you want to convert km/hr into m/s then multiply with 5/18.
For example: 108 km/hr = 108km/hr*5/18 = 30m/s.
If you want to convert m/s into km/hr then multiply with 18/5.
For example: 5 m/s = 5m/s*18/5 = 18km/hr.
If you want to convert km/hr into m/s then multiply with 5/18.
For example: 108 km/hr = 108km/hr*5/18 = 30m/s.
Nithish raj said:
4 years ago
125/10 is for speed divide by time taken,
And 18/5 is to convert meter to kilometre
So that 125/10 is 25/2.
Multiply 25/2 by 18/5 to get in kilometre so it gets 45km/hr.
And the man running speed is 5km/hrs.
So, 45 + 5 is 50km/hrs.
And 18/5 is to convert meter to kilometre
So that 125/10 is 25/2.
Multiply 25/2 by 18/5 to get in kilometre so it gets 45km/hr.
And the man running speed is 5km/hrs.
So, 45 + 5 is 50km/hrs.
(1)
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