In the previous question, the mean velocity of the rocket reaching the maximum height is :

Explanation

To solve the problem of finding the mean velocity of the rocket reaching the maximum height, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Displacement**:
The displacement when the rocket reaches its maximum height is given as \( h_{max} = 60 \) kilometers.
To convert this into meters, we use the conversion factor \( 1 \text{ km} = 1000 \text{ m} \):
\[ h_{max} = 60 \text{ km} \times 1000 \text{ m/km} = 60000 \text{ m} \]

2. **Determine the Time Taken**:
From the graph mentioned in the transcript, we know that the time taken to reach the maximum height is \( t = 120 \) seconds.

3. **Calculate the Mean Velocity**:
The mean velocity (\( v_{avg} \)) can be calculated using the formula:
\[ v_{avg} = \frac{\text{Displacement}}{\text{Time}} \]
Substituting the values we have:
\[ v_{avg} = \frac{60000 \text{ m}}{120 \text{ s}} \]

4. **Perform the Calculation**:
Now, we can simplify the calculation:
\[ v_{avg} = \frac{60000}{120} = 500 \text{ m/s} \]

5. **Conclusion**:
Therefore, the mean velocity of the rocket reaching the maximum height is \( 500 \text{ m/s} \).

### Final Answer:
The mean velocity of the rocket reaching the maximum height is \( 500 \text{ m/s} \).