Find the time taken by a train 180m long, running at 72 km/h in crossing an electrical pole.

Answer

To solve the problem of finding the time taken by a train 180 meters long, running at 72 km/h, to cross an electrical pole, we can follow these steps:

### Step 1: Convert the speed from km/h to m/s
The speed of the train is given as 72 km/h. To convert this speed into meters per second (m/s), we can use the conversion factor:

\[ 1 \text{ km/h} = \frac{5}{18} \text{ m/s} \]

So, we can calculate the speed in m/s as follows:

\[ \text{Speed in m/s} = 72 \times \frac{5}{18} \]

### Step 2: Calculate the speed in m/s
Now, let's perform the calculation:

\[ \text{Speed in m/s} = 72 \times \frac{5}{18} = 72 \times \frac{5}{18} = 20 \text{ m/s} \]

### Step 3: Use the formula for time
When a train crosses an electrical pole, it covers a distance equal to its own length. Therefore, the distance to be covered is 180 meters. The formula to calculate time is:

\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]

### Step 4: Substitute the values into the formula
Now, we can substitute the values into the formula:

\[ \text{Time} = \frac{180 \text{ m}}{20 \text{ m/s}} \]

### Step 5: Calculate the time
Now we perform the division:

\[ \text{Time} = \frac{180}{20} = 9 \text{ seconds} \]

### Conclusion
The time taken by the train to cross the electrical pole is **9 seconds**.

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