Understanding Speed Calculation
To calculate the speed of a car that travels 150 km in 3 hours, we need to use the formula for speed:

Speed Formula
Speed = Distance ÷ Time
Where:
- Distance = 150 km
- Time = 3 hours

Step 1: Calculate Speed in km/h
- Plugging the values into the formula:
Speed = 150 km ÷ 3 hours = 50 km/h
This means the car travels at a speed of 50 kilometers per hour.

Step 2: Convert Speed to km/s
To find the speed in kilometers per second, we need to convert hours into seconds:
- 1 hour = 3600 seconds

Step 3: Calculate Speed in km/s
- Now, converting the speed from km/h to km/s:
Speed in km/s = Speed in km/h ÷ 3600
- Substituting the speed:
Speed in km/s = 50 km/h ÷ 3600 = 0.01389 km/s

Final Result
The speed of the car is approximately:
- **0.01389 kilometers per second**

Summary
- The car travels **150 km** in **3 hours**.
- The speed calculated is **50 km/h**.
- Converting this to kilometers per second gives us approximately **0.01389 km/s**.
This detailed breakdown helps in understanding how to derive speed in different units, essential for various competitive exams, including UPSC.