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 37 of 48.
Ganesh said:
7 years ago
Anyone please explain about relative speed.
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).
Akeer said:
7 years ago
@Ganesh.
The Relative means related to speed. The two trains are in which direction moving based on that we have to take the speed to add or sub.
The Relative means related to speed. The two trains are in which direction moving based on that we have to take the speed to add or sub.
Dhivya said:
7 years ago
L(train) = (speed of train-speed of object) * time.
125m = (St-5)km/hr * 10s,
112.5 * 18/5 = st - 5,
St = 50km/hr.
125m = (St-5)km/hr * 10s,
112.5 * 18/5 = st - 5,
St = 50km/hr.
Farheen said:
7 years ago
To convert km/hr to m/sec we multiply it with 5/18.
If we are converting m/sec to km/hr we multiply it 18/5.
If we are converting m/sec to km/hr we multiply it 18/5.
Vipin said:
7 years ago
Hi, I am not getting this. Please anyone help me to get it.
Robi said:
7 years ago
@Omkar Tanpure.
What is the relative speed? And why 45 is called relative speed? Please explain me.
What is the relative speed? And why 45 is called relative speed? Please explain me.
Ramya said:
7 years ago
Can anyone Explain this problem to me? I didn't understand this.
Chandan Azad said:
7 years ago
T(time required) = Lt(length of train) + Lo(length of object)/ Ut(speed of Train)+,-Uo(speed of object) .
("-" when train and object goes in same direction.
"+" when train and object goes in opposite direction.)
10=(125+0)/(Ut-5*5/18).
Ut=125/9.
Ut=(125/9)*(18/5).
Ut=50km/hr.
("-" when train and object goes in same direction.
"+" when train and object goes in opposite direction.)
10=(125+0)/(Ut-5*5/18).
Ut=125/9.
Ut=(125/9)*(18/5).
Ut=50km/hr.
Hari kumar said:
7 years ago
50 is the right answer.
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