The odometer of a car reads ` 2000 km ` at the start of a trip and `2400 km` at the end of the trip . If the trip took `8 h` , calculate the average speed of the car in `km//h and m//s`.

Options

A. 13.9 m/s
B. 12.9 m/s
C. 10.9 m/s
D. 10 m/s

Explanation

To solve the problem step by step, we will calculate the average speed of the car in both kilometers per hour (km/h) and meters per second (m/s).

### Step 1: Identify the initial and final distances
- Initial distance (di) = 2000 km
- Final distance (df) = 2400 km

### Step 2: Calculate the total distance traveled
The total distance traveled can be calculated using the formula:
\[ \text{Total Distance} = \text{Final Distance} - \text{Initial Distance} \]
\[ \text{Total Distance} = df - di = 2400 \, \text{km} - 2000 \, \text{km} = 400 \, \text{km} \]

### Step 3: Identify the total time taken
- Total time (t) = 8 hours

### Step 4: Calculate the average speed in km/h
The average speed can be calculated using the formula:
\[ \text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}} \]
\[ \text{Average Speed} = \frac{400 \, \text{km}}{8 \, \text{h}} = 50 \, \text{km/h} \]

### Step 5: Convert average speed from km/h to m/s
To convert km/h to m/s, we use the conversion factor:
\[ 1 \, \text{km/h} = \frac{1000 \, \text{m}}{3600 \, \text{s}} \]
Thus, to convert 50 km/h to m/s:
\[ \text{Average Speed in m/s} = 50 \, \text{km/h} \times \frac{1000 \, \text{m}}{3600 \, \text{s}} \]
\[ \text{Average Speed in m/s} = 50 \times \frac{1000}{3600} \]
\[ \text{Average Speed in m/s} = 50 \times 0.27778 \approx 13.89 \, \text{m/s} \]

### Final Results
- Average speed in km/h = 50 km/h
- Average speed in m/s ≈ 13.89 m/s