In net force on a system is zero then

Options

A. its momentum is conserved
B. Its kinetic energy may increase
C. The acceleration of it’s a constitutent particle may be non - zero
D. All of these

Answer

To solve the question, "If the net force on a system is zero, then...", we will analyze the implications of having a net force of zero on a physical system.

### Step-by-Step Solution:

1. **Understanding Net Force**:
The net force on a system is the vector sum of all the forces acting on it. If the net force is zero, it indicates that the forces are balanced.

**Hint**: Remember that balanced forces mean that the object is either at rest or moving at a constant velocity.

2. **Conservation of Momentum**:
According to Newton's first law of motion, if the net force acting on an object is zero, the momentum of that object remains constant. Therefore, the momentum of the system is conserved.

**Hint**: Think about how momentum is defined and how it relates to forces acting on an object.

3. **Translational Motion**:
With zero net force, the translational motion of the system can continue. The object can either remain at rest or move with a constant velocity. The speed of translation does not change.

**Hint**: Consider the implications of constant velocity on the motion of an object.

4. **Rotational Motion**:
The system may still have rotational motion. Even if the net force is zero, the object can rotate around an axis. The rotational kinetic energy can be present and may not change if there are no external torques acting on the system.

**Hint**: Recall how rotational motion is independent of translational motion.

5. **Acceleration of Particles**:
While the net force is zero, the acceleration of individual particles within the system may not be zero, especially if they are undergoing rotational motion. Angular acceleration can occur even if the linear acceleration is zero.

**Hint**: Think about how different types of motion can coexist in a system.

6. **Conclusion**:
Therefore, if the net force on a system is zero, the following statements are true:
- Momentum is conserved.
- The translational motion can continue at a constant speed.
- Rotational motion can exist, and the kinetic energy associated with rotation can be non-zero.
- Individual particles may have non-zero acceleration due to rotation.

### Final Answer:
If the net force on a system is zero, then the momentum is conserved, translational motion continues at constant speed, rotational motion can exist, and individual particle accelerations may be non-zero.