How long does it take for a fast train 150m long to pass the 850m long bridge with a speed of 72km / h?

To find the required duration of the movement of a fast train across the bridge, we will use the formula: t = S / V = (Lp + Lm) / Vp.

The values of the variables: Lp – the length of the fast train (Lp = 150 m); Lm is the length of the bridge (Lm = 850 m); Vp – speed of a fast train (Vp = 72 km / h = 20 m / s).

Let’s make a calculation: t = (Lp + Lm) / Vp = (150 + 850) / 20 = 50 s.

Answer: The fast train must pass the bridge in 50 seconds.