Concept:Newton's first law states that an object continues in its state of rest or uniform linear motion unless acted upon by an unbalanced external force.
Explanation:Uniform linear motion means constant velocity, including both constant speed and constant direction.
From Newton's first law, if the net external force is zero, the body will not accelerate.
Therefore, in uniform linear motion, all forces acting on the body balance out, making the net force equal to zero.
Option A is incorrect because Newton's first law does not restrict motion to translation only.
Option B is incorrect because a body at rest can still have forces acting on it, provided they cancel out.
Option D is incorrect because inertia is the property of mass, not the same as weight.
Thus, the correct statement is that the net force acting in uniform linear motion is zero.
Answer:C. The net force acting in uniform linear motion is zero.