Question

24. A train 50 m long passes over a bridge at a
velocity of 30 km/h. If it takes 36 s to cross
the bridge, the length of the bridge will be
(a) 100 m
(b) 200 m
(c) 250 m (d) 300 m​

Answer 1

Answer:option (c) 250m

Explanation:

We know v=d/t

V = velocity

d=displacement

t=time

30km/h *5/18 = 50 + l /36

l = length of train

Solve it and you will get answer

Answer 2

Question:

24. A train 50 m long passes over a bridge at a  velocity of 30 km/h. If it takes 36 s to cross  the bridge, the length of the bridge will be

(a) 100 m

(b) 200 m

(c) 250 m

(d) 300 m​

Answer:

(c) 250 m.

Given:

The length of the train is 50 m.

The velocity of the train is 30 km/h.

The train takes 36 seconds to cross the bridge.

To find:

The length of the bridge.

Explanation:

The velocity of the train is 30 km/h.

∴ The velocity of the train in m/s _

$(30 \times \dfrac{5}{18})\\ \\= (5 \times \dfrac{5}{3})\\ \\= (\dfrac{25}{3}) m/s$

The velocity of the train = The speed of the train = $\frac{25}{3}$ m/s.

The train takes 36 seconds to cross the bridge.

We know that,

Speed = (Distance/Time)

⇒ Distance = (Speed × Time)

⇒ Distance  = ( $\frac{25}{3}$ × 36)

                     = (25 × 12)

                    = 300 m.

∴ Total distance covered by the train is 300 m.

The length of the train is 50 m.

∴ The length of the bridge is _

(300 - 50) m

= 250 m.

∴ The length of the train is 205 m.

Hence, option (c) 250 m, is the correct answer.