A person driving a car with a speed 72 km/h suddenly sees a boy crossing the road. If the distance moved by car, before the person applies brakes is 5 m, the reaction time of the person is

Options

A. 0.5 s
B. 0.10 s
C. 10 s
D. 0.25 s

Answer

To solve the problem, we need to determine the reaction time of the driver based on the information provided.

### Step-by-Step Solution:

1. **Convert the speed from km/h to m/s**:
The speed of the car is given as 72 km/h. To convert this to meters per second (m/s), we use the conversion factor:
\[ \text{Speed in m/s} = \text{Speed in km/h} \times \frac{5}{18} \]
So,
\[ \text{Speed} = 72 \times \frac{5}{18} = 20 \text{ m/s} \]

2. **Identify the distance moved before applying brakes**:
The problem states that the car moves a distance of 5 meters before the driver applies the brakes.

3. **Calculate the time taken to cover the distance**:
The time taken to cover a distance can be calculated using the formula:
\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]
Substituting the values we have:
\[ \text{Time} = \frac{5 \text{ m}}{20 \text{ m/s}} = 0.25 \text{ seconds} \]

4. **Conclusion**:
The reaction time of the person is 0.25 seconds.

### Final Answer:
The reaction time of the person is **0.25 seconds**.

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