If the displacement x of a particle of mass m is directly proportionalto time, net force acting on it is ________________.

Answer

To solve the problem, we need to analyze the relationship between displacement, velocity, acceleration, and force acting on a particle of mass \( m \).

### Step-by-Step Solution:

1. **Understanding the relationship**: The problem states that the displacement \( x \) of a particle is directly proportional to time \( t \). This can be mathematically expressed as:
\[ x = kt \]
where \( k \) is a constant.

2. **Finding velocity**: Velocity \( v \) is defined as the rate of change of displacement with respect to time. Therefore, we differentiate \( x \) with respect to \( t \):
\[ v = \frac{dx}{dt} = \frac{d(kt)}{dt} = k \]
Since \( k \) is a constant, the velocity \( v \) is constant.

3. **Finding acceleration**: Acceleration \( a \) is defined as the rate of change of velocity with respect to time. We differentiate \( v \) with respect to \( t \):
\[ a = \frac{dv}{dt} = \frac{d(k)}{dt} = 0 \]
Since \( k \) is a constant, the acceleration \( a \) is zero.

4. **Applying Newton's second law**: According to Newton's second law, the net force \( F \) acting on an object is given by:
\[ F = m \cdot a \]
Substituting the value of acceleration:
\[ F = m \cdot 0 = 0 \]

5. **Conclusion**: Therefore, the net force acting on the particle is:
\[ \text{Net Force} = 0 \]

### Final Answer:
The net force acting on the particle is **0**.