Question

A $60m$ long train moving on a straight level track passes a pole in $5s$. Find the speed of the train and the time it will take to cross a $540m$ long bridge.

• A. $13m{s}^{-1}$, $40s$
• B. $25m{s}^{-1}$, $30s$
• C. $12m{s}^{-1}$, $50s$
• D. $15m{s}^{-1}$, $65s$

Answer 1

The correct option is C $12m{s}^{-1}$, $50s$

Given:
Length of the train, $D=60m$,
Time taken to cross the pole, $T=5s$,
Length of the bridge $=540m$

$\text{Speed of the train, s}=\frac{\text{D}}{T}$

$\text{Speed of the train, s}=\frac{60}{5}=12m{s}^{-1}$

Now, distance to be covered to cross a $540m$ long bridge is sum of Length of the train and Length of the bridge.
$d=60+540=600m$

$\therefore \text{Time taken}=\frac{\text{d}}{\text{s}}$

$\text{Time taken}=\frac{600}{12}=50s$

$\therefore$ Speed of the train is $12m{s}^{-1}$ and the time it will take to cross the bridge is $50s$.