In Newtonian mechanics, which force is responsible for producing the acceleration of an object according to Newton's second law?

• A. The normal force only
• B. The net (resultant) external force acting on the object
• C. The object's weight only
• D. Any single force acting on the object, regardless of other forces

Answer: (B)

Verified step by step guidance

1. Recall Newton's second law, which states that the acceleration \(\vec{a}\) of an object is directly proportional to the net external force \(\vec{F}_{\text{net}}\) acting on it and inversely proportional to its mass \(m\). This is mathematically expressed as \(\vec{F}_{\text{net}} = m \vec{a}\).
2. Understand that the 'net external force' means the vector sum of all external forces acting on the object, not just a single force like the normal force or the object's weight.
3. Recognize that individual forces such as the normal force or weight contribute to the net force, but it is their combined effect (resultant force) that determines the acceleration.
4. Note that if multiple forces act on an object, you must add them vectorially to find the net force before applying Newton's second law.
5. Conclude that the force responsible for producing acceleration is the net (resultant) external force acting on the object, as per Newton's second law.