A particle is fired with a speed of 20 km/h. The speed with which it will move in intersteller space is

Options

A. `16 . 5 `
B. `11 . 2`
C. 10
D. `8 . 8 `

Explanation

To solve the problem of finding the speed with which a particle will move in interstellar space after being fired with an initial speed of 20 km/h, we can follow these steps:

### Step-by-Step Solution:

1. **Convert Speed to Consistent Units**:
The initial speed of the particle is given as 20 km/h. We need to convert this speed into km/s for consistency with the escape velocity, which is given in km/s.
\[ 20 \text{ km/h} = \frac{20}{3600} \text{ km/s} \approx 0.00556 \text{ km/s} \]

2. **Identify Escape Velocity**:
The escape velocity from the Earth is approximately 11.2 km/s. This is the minimum speed needed for an object to break free from Earth's gravitational pull without any additional propulsion.

3. **Compare Initial Speed with Escape Velocity**:
Since the initial speed of the particle (0.00556 km/s) is much less than the escape velocity (11.2 km/s), the particle will not escape Earth's gravitational influence.

4. **Conclusion**:
Since the particle does not reach escape velocity, it will not move into interstellar space. Instead, it will fall back to Earth. Therefore, the speed with which it will move in interstellar space is effectively 0 km/s.

### Final Answer:
The speed with which the particle will move in interstellar space is **0 km/s**.

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