Time, Speed & Distance • Topic 3 of 4

Trains

A train crossing a pole (a point) travels its own length; crossing a platform/bridge travels (train length + platform length). Two trains crossing each other travel the sum of their lengths at the relative speed (sum if opposite, difference if same direction). Convert km/h to m/s with 5/18 since lengths are in metres and times in seconds.

✅ Solved examples

1. A 150 m train at 54 km/h crosses a pole in how many seconds?
Speed 54 x 5/18 = 15 m/s; time = 150/15 = 10 s.
2. A 200 m train at 72 km/h crosses a 100 m platform. Time?
Speed 20 m/s; distance 300 m; time = 15 s.
3. Two trains 120 m and 80 m, speeds 40 and 50 km/h, opposite directions. Time to cross?
Rel speed 90 km/h = 25 m/s; distance 200 m; time = 8 s.
4. A train crosses a 250 m bridge in 30 s at 30 m/s. Train length?
Distance 900 m; train = 900 - 250 = 650 m.

✏️ Practice — try these, take hints as needed

1. 180 m train at 36 km/h crosses a pole in?
36 x 5/18 = 10 m/s.
180/10.
—
18 s
2. 250 m train at 90 km/h crosses 150 m platform?
25 m/s; distance 400.
400/25.
—
16 s
3. Two trains 100 m each, 36 and 54 km/h, opposite. Time?
Rel 90 km/h = 25 m/s.
Distance 200.
—
8 s
4. Train 200 m crosses 300 m bridge in 25 s. Speed (m/s)?
Distance 500.
500/25.
—
20 m/s
5. Train at 20 m/s crosses pole in 9 s. Length?
d = s x t.
20 x 9.
—
180 m

📝 Topic test — 8 questions

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