In what time (in seconds) will a train 60 metres long, running at a speed of 36 km/hr, completely pass a stationary telegraph post beside the track?

Introduction / Context:
This is a basic train and distance question. When a train passes a telegraph post or any fixed point, the distance relevant for the passing is simply the length of the train. We are given the speed and length of the train and need to find the time taken to pass the post.

Given Data / Assumptions:
- Length of the train = 60 m.
- Speed of the train = 36 km/hr.
- The telegraph post is a fixed point with negligible width.
- The train moves with constant speed throughout the crossing.

Concept / Approach:
Time is given by time = distance / speed. The distance is the train length, and the speed must be in metres per second to match the distance units. We convert the speed from km/hr to m/s, then apply the formula to find the time in seconds.

Step-by-Step Solution:
Step 1: Distance to be covered relative to the post = length of the train = 60 m.Step 2: Convert speed from km/hr to m/s: 36 km/hr = 36 * (5 / 18) m/s.Step 3: Compute the conversion: 36 * (5 / 18) = (36 / 18) * 5 = 2 * 5 = 10 m/s.Step 4: Use time = distance / speed: time = 60 / 10 seconds.Step 5: This gives time = 6 seconds.Step 6: Therefore, the train takes 6 seconds to pass the telegraph post completely.

Verification / Alternative check:
We can quickly sanity-check the result. At 10 m/s, a train covers 10 metres each second. To travel 60 metres, it needs 60 / 10 = 6 seconds. This simple mental check matches the detailed calculation exactly.

Why Other Options Are Wrong:
9, 8, 7, and 5 seconds would correspond to effective speeds of 60 / 9, 60 / 8, 60 / 7, and 60 / 5 m/s respectively, none of which equal the actual 10 m/s converted from 36 km/hr. Only 6 seconds is consistent with the given length and speed.

Common Pitfalls:
Typical errors include incorrectly converting km/hr to m/s (for example, multiplying by 18 / 5), or using a wrong distance such as assuming a platform instead of a post. Remember: for crossing a fixed point, only the train's own length matters.

Final Answer:
The 60 metre long train will pass the telegraph post completely in 6 seconds.