Question

If a train crossed a pole at a speed of 60km/hr in 30 seconds, find its length.

a)1000 m
b)900 m
c)750 m
d)500 m

Answer 1

Hint: Use the speed and time given in question to find the distance or in this case length.

Distance = speed x time.

Complete step-by-step answer:


To solve for distance, use the formula for distance d = st, or distance equals speed times time. Rate and speed are similar since they both represent some distance per unit time like miles per hour or kilometres per hour. If rate r is the same as speed s, r = s = $\dfrac{d}{t}$ .


 We know that it takes 30 seconds for the train to pass the pole. Since the length of pole is negligent compared to that of the train, we assume that the entire length is that of the train.


As the train passes through the pole so that means that between the time period an entire length of the train passed

So, using the formula Distance = Speed x time.

But first we have to make both units the same.

Time = 30 seconds = .5 mins = $\dfrac{.5}{60}$ hrs

Now that we have the same units, we make further calculations.

Distance = 60 x$\dfrac{.5}{60}$ = .5 km


So, the length of the train is 500 m.


Hence option d is the correct answer.


Note: While handling this problem make sure you convert the units to the same level or you will get a wrong answer. Alternatively, you can also convert speed into m/s and get the same result.