In the context of forces and free-body diagrams, which of the following is a noncontact force?

• A. Gravitational force
• B. Frictional force
• C. Normal force
• D. Tension force

Answer: (A)

Verified step by step guidance

1. Understand the difference between contact and noncontact forces: Contact forces require physical touching between objects, while noncontact forces act at a distance without direct contact.
2. Identify the nature of each force listed: Frictional force, normal force, and tension force all arise from physical contact between objects.
3. Recognize that gravitational force is a force that acts between masses even when they are not touching, making it a classic example of a noncontact force.
4. Recall that gravitational force is described by Newton's law of universal gravitation, which states that every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.
5. Conclude that among the options given, gravitational force is the noncontact force because it acts over a distance without requiring physical contact.