A spaceship continues moving in space with constant speed because

Options

A. no force of friction due to air acts on it
B. no force of gravitation acts on it
C. its mass is zero in space
D. none of these

Explanation

To solve the question "A spaceship continues moving in space with constant speed because," we need to analyze the options provided and understand the principles of motion in space.

### Step-by-step Solution:

1. **Understanding Motion in Space**:
- In space, a spaceship can move without any significant resistance. This is because space is a near vacuum, meaning there is no air to create friction.

2. **Analyzing the Options**:
- **Option 1**: "No force of friction due to air acts on it."
- This option is true because there is no air in space, so there is no friction acting on the spaceship. However, this alone does not explain why it continues moving at constant speed.

- **Option 2**: "No force of gravitation acts on it."
- This option is also true, but it depends on the spaceship's location. If the spaceship is far from any massive objects (like planets), then the gravitational force is negligible. If there is no gravitational force acting on it, then there is no net force acting on the spaceship, allowing it to maintain constant speed.

- **Option 3**: "Its mass is 0 in spaceship."
- This option is incorrect. The mass of an object is an intrinsic property and cannot be zero. The spaceship has mass regardless of its location in space.

- **Option 4**: "None of these."
- This option is not correct since we have identified valid reasons in the previous options.

3. **Conclusion**:
- The most accurate answer is **Option 2**: "No force of gravitation acts on it." This is because, in the absence of any net external forces (including gravitational forces), the spaceship can continue to move at a constant speed according to Newton's First Law of Motion.

### Final Answer:
The spaceship continues moving in space with constant speed because **no force of gravitation acts on it**.