Static Friction

Definition

Static friction is the force that resists the relative motion between two surfaces in contact when they are not moving with respect to each other. It is the maximum force that can be applied before the surfaces start to slide against each other.

5 Must Know Facts For Your Next Test

1. Static friction is the maximum frictional force that can be applied before the surfaces start to slide against each other.
2. Static friction is directly proportional to the normal force between the surfaces and the coefficient of static friction.
3. Static friction is independent of the area of contact between the surfaces, as long as the surfaces are in full contact.
4. Static friction helps objects remain at rest and prevents them from sliding down inclined planes.
5. Static friction plays a crucial role in uniform circular motion, as it provides the necessary centripetal force to keep an object moving in a circular path.

Review Questions

• Explain how static friction relates to Newton's First Law of Motion (Inertia).
  • Static friction is the force that helps an object at rest remain at rest, in accordance with Newton's First Law of Motion. When an object is at rest, static friction acts to counteract any applied force, preventing the object from moving. This static friction force is equal in magnitude and opposite in direction to the applied force, allowing the object to maintain its state of rest or uniform motion.
• Describe the role of static friction in the context of inclined planes.
  • On an inclined plane, static friction is the force that prevents an object from sliding down the surface. The static friction force acts parallel to the inclined surface, opposing the component of the object's weight that is directed down the slope. As long as the static friction force is greater than or equal to this component of the weight, the object will remain stationary on the inclined plane.
• Analyze the importance of static friction in the context of uniform circular motion.
  • In uniform circular motion, static friction is the force that provides the necessary centripetal force to keep an object moving in a circular path. The static friction force acts perpendicular to the object's velocity, causing it to accelerate towards the center of the circle. Without this static friction force, the object would continue in a straight line, violating the requirement for uniform circular motion.

Related terms

Kinetic Friction: The force that resists the relative motion between two surfaces that are sliding against each other.

Coefficient of Friction: A dimensionless scalar quantity that describes the ratio of the friction force between two surfaces to the normal force pressing them together.

Normal Force: The force exerted perpendicular to the surface of contact between two objects, which is responsible for the frictional force.