A train of 150 m length is going towards north direction at a speed of 10 m/s. A bird flies at a speed of 5 m/s towards south direction paral­lel to the railway track. The time taken by the bird to cross the train is equal to

Options

A. 20 sec
B. 16 sec
C. 12 sec
D. 10 sec

Explanation

To solve the problem of how long it takes for the bird to cross the train, we can follow these steps:

### Step 1: Understand the scenario
We have a train that is 150 meters long moving north at a speed of 10 m/s, and a bird flying south at a speed of 5 m/s. We need to determine how long it takes for the bird to completely cross the train.

### Step 2: Determine the relative speed
Since the train and the bird are moving in opposite directions, we can find the relative speed by adding their speeds together:
- Speed of the train = 10 m/s (north)
- Speed of the bird = 5 m/s (south)

**Relative speed = Speed of the train + Speed of the bird**
Relative speed = 10 m/s + 5 m/s = 15 m/s

### Step 3: Calculate the time taken to cross the train
To find the time taken for the bird to cross the train, we use the formula:
\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]

In this case, the distance is the length of the train (150 m) and the speed is the relative speed (15 m/s):
\[ \text{Time} = \frac{150 \text{ m}}{15 \text{ m/s}} \]

### Step 4: Perform the calculation
\[ \text{Time} = 10 \text{ seconds} \]

### Conclusion
The time taken by the bird to cross the train is **10 seconds**.