External force

Definition

An external force is a force that originates from outside a system and influences the motion or behavior of that system. In classical mechanics and electrical circuits, external forces can dictate how objects move, change direction, or experience changes in energy. Understanding external forces is essential to analyzing system dynamics, as they often determine how systems respond to various inputs and interactions.

5 Must Know Facts For Your Next Test

1. External forces can be categorized into contact forces (like friction and tension) and non-contact forces (like gravitational and electromagnetic forces).
2. In classical mechanics, an object's acceleration is directly proportional to the net external force acting on it and inversely proportional to its mass, as described by Newton's second law: $$F = ma$$.
3. In electrical circuits, external forces like voltage influence the flow of current, while resistive forces like resistance impede it.
4. The presence of external forces can lead to changes in momentum, which affects not only the motion of individual objects but also interactions between multiple systems.
5. When analyzing systems in equilibrium, it is crucial to consider how external forces balance internal forces to maintain stability.

Review Questions

• How do external forces impact the motion of objects in classical mechanics?
  • External forces significantly influence the motion of objects by determining their acceleration and trajectory. According to Newton's second law, the net external force acting on an object equals the mass of that object multiplied by its acceleration. This means that if an external force is applied, it will cause the object to accelerate in the direction of that force. Understanding this relationship helps explain how different factors like friction or gravity can alter an object's movement.
• In what ways do external forces interact with internal forces in a system at equilibrium?
  • In a system at equilibrium, external forces must balance out the internal forces to ensure stability. For instance, if a force is applied externally, it creates a net force that needs to be countered by internal forces within the system. If these forces are not balanced, the system will experience acceleration or movement away from equilibrium. Analyzing these interactions allows us to understand stability in physical systems, whether they are mechanical structures or electrical circuits.
• Evaluate the role of external forces in both mechanical systems and electrical circuits and their influence on energy transfer.
  • External forces play a critical role in both mechanical systems and electrical circuits by driving energy transfer and influencing system behavior. In mechanical systems, forces such as tension or gravitational pull determine how objects move and interact. In electrical circuits, electromotive force acts as an external influence that drives current flow. By evaluating these roles, we see how external forces not only initiate motion but also impact energy efficiency and conservation within different types of systems.

Related terms

net force: The overall force acting on an object when all individual forces acting on it are combined.

inertia: The tendency of an object to resist changes in its state of motion; related to its mass.

electromotive force (EMF): The energy provided per charge by a source, such as a battery, driving the current in an electrical circuit.