Question

A person is standing on a railway bridge which is 200m long. he observes that a train crosses the bridge in 30 seconds but it crosses him in 10 seconds. find the length of train and its speed.

Answer 1

S = D*T

T = 30 s

S = (L+200)/30 m/s

T = 10 s

S = L/10 m/s

We know that the speed is same so,

S = S = (L+200)/30 m/s

= L/10 m/s

(L+200)*10

L*30

10L+2000 = 30L

2000 = 30L - 10 L = 20 L

L = 2000/20 = 100 m

S = 100/10

= 10 m/s

Notes: D is the length of the train.

If there is any confusion please leave a comment below.

Answer 2

let the length of the train be x meters.

the train covers x meters in 10 sec and (x+200) meters in 30 sec.

we know that , speed=distance/time.

x/10 = (x+200)/30

x=100 m.

the length of the train is 100 m.

the speed of the train = distance/time

                                    =100/10

       speed of the train=10 m/s