In the context of Newton's First and Second Laws, what is the definition of the net force acting on an object?

• A. The object's mass multiplied by its velocity, $m\cdot v$.
• B. The largest single force acting on the object.
• C. The force an object exerts on its surroundings due to its weight, $m\cdot g$.
• D. The vector sum of all external forces acting on the object.

Answer: (D)

Verified step by step guidance

1. Recall Newton's First Law, which states that an object remains at rest or in uniform motion unless acted upon by a net external force.
2. Understand that Newton's Second Law quantifies this net force as the cause of acceleration, expressed as \(\mathbf{F}_{\text{net}} = m \mathbf{a}\), where \(m\) is mass and \(\mathbf{a}\) is acceleration.
3. Recognize that the net force is not just a single force but the vector sum of all external forces acting on the object, meaning all forces are combined considering their directions.
4. Note that the net force differs from simply the largest force or the weight force \(m \cdot g\), as it accounts for all forces, including friction, tension, applied forces, etc.
5. Therefore, the net force is defined as the vector sum of all external forces acting on the object, which determines the object's acceleration according to Newton's Second Law.