A train of `150 m` length is going towards north direction at a speed of `10 ms^-1`. A parrot flies at a speed of `5 ms^-1` towards south direction parallel to the railway track. The time taken by the parrot to cross the train is equal to.

Options

A. `12 s`
B. `8 s`
C. `15 s`
D. `10 s`

Explanation

To solve the problem of how long it takes for the parrot 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. A parrot is flying south at a speed of 5 m/s. We need to find the time it takes for the parrot to completely cross the train.

### Step 2: Determine the relative speed
Since the train and the parrot are moving in opposite directions, we can find the relative speed of the parrot with respect to the train by adding their speeds:

\[ \text{Relative speed} = \text{Speed of the train} + \text{Speed of the parrot} = 10 \, \text{m/s} + 5 \, \text{m/s} = 15 \, \text{m/s} \]

### Step 3: Calculate the time taken to cross the train
The time taken to cross the train can be calculated using 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 we just calculated (15 m/s):

\[ \text{Time} = \frac{150 \, \text{m}}{15 \, \text{m/s}} = 10 \, \text{s} \]

### Step 4: Conclusion
Thus, the time taken by the parrot to cross the train is **10 seconds**.

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