Forces shape our physical world, dictating how objects move and interact. From the keeping us on the ground to in ropes and between surfaces, these invisible pushes and pulls govern everyday phenomena.
Newton's laws provide a framework for understanding and predicting motion. By identifying forces, drawing diagrams, and applying these laws, we can solve complex problems involving multiple objects and forces in various scenarios.
Types of Forces
Normal and tension forces
acts perpendicular to the surface an object is in contact with prevents the object from sinking into the surface (book on a table, person standing on the ground)
is exerted by a taut rope, string, or cable pulls along the length of the object (rope pulling a box, cable supporting a bridge)
Friction force opposes the relative motion between two surfaces in contact
Applying Newton's Laws
Applications of Newton's laws
: Objects maintain their state of motion unless acted upon by an unbalanced force
: [F = ma](https://www.fiveableKeyTerm:F_=_ma), equals mass times acceleration
Net force is the vector sum of all forces acting on an object
: Action-reaction force pairs, forces always occur in equal and opposite pairs
Problem-solving steps:
Identify all forces acting on the object(s)
Draw a for each object, representing forces as vectors (force vectors)
Choose a coordinate system and decompose forces into components if necessary
Apply Newton's second law to each object, setting up equations for each coordinate
Solve the system of equations to find unknown quantities (acceleration, tension force)
Weight components in force problems
is the force due to gravity, [W = mg](https://www.fiveableKeyTerm:W_=_mg), where W is , m is mass, and g is the acceleration due to gravity
On an , weight can be decomposed into components:
Parallel component: W∥=Wsinθ, where θ is the angle of the incline with respect to the horizontal contributes to the net force causing the object to accelerate down the incline
Perpendicular component: W⊥=Wcosθ balanced by the normal force exerted by the incline on the object
Equilibrium and Force Balance
occurs when the net force acting on an object is zero
: object is at rest and remains at rest
: object moves with constant velocity
In equilibrium, the vector sum of all forces (including normal, tension, weight, and friction) must equal zero
Key Terms to Review (24)
Dynamic equilibrium: Dynamic equilibrium occurs when an object is in motion but remains in a state where all the forces acting on it are balanced. This results in no change in velocity, maintaining constant speed and direction.
Dynamic Equilibrium: Dynamic equilibrium is a state of balance in a system where opposing forces or processes are occurring simultaneously, resulting in an overall stable condition. This term is particularly relevant in the context of understanding normal forces, tension, and the first condition for equilibrium in physics.
Electrostatic equilibrium: Electrostatic equilibrium occurs when the charges within a conductor are at rest, resulting in no net movement of charge. In this state, the electric field inside the conductor is zero and any excess charge resides on the surface.
Equilibrium: Equilibrium is a state of balance or stability, where the forces acting on a system are in a state of balance, and the system remains at rest or in a constant state of motion. This concept is fundamental in various areas of physics, including mechanics, thermodynamics, and electromagnetism.
F = ma: F = ma is a fundamental equation in physics that describes the relationship between force (F), mass (m), and acceleration (a). It states that the force acting on an object is equal to the product of the object's mass and its acceleration. This equation is central to understanding the dynamics of objects in motion and is applicable in various contexts, including the topics of normal force, tension, and centripetal acceleration.
Force Vector: A force vector is a mathematical representation of a force that includes both the magnitude (size) and direction of the force acting on an object. It is a fundamental concept in physics that describes the combined effect of multiple forces acting on a body.
Free-body diagram: A free-body diagram is a graphical illustration used to visualize the forces acting on an object. It simplifies complex systems into a single object with vectors representing all external forces.
Free-Body Diagram: A free-body diagram is a visual representation of the forces acting on an object or a system in a given situation. It is a crucial tool used in the study of mechanics and the application of Newton's laws of motion, as it helps to identify and analyze the forces that influence the motion or equilibrium of a body or system.
Friction: Friction is the resistive force that occurs when two surfaces interact, opposing the relative motion between them. It acts parallel to the surfaces in contact and can be either static or kinetic.
Inclined Plane: An inclined plane is a simple machine that consists of a flat surface tilted at an angle, used to raise or lower objects by applying a force parallel to the surface. It is one of the six classical simple machines and plays a crucial role in various physical phenomena and applications.
Net Force: Net force is the vector sum of all the individual forces acting on an object. It represents the overall force that determines the object's acceleration or lack thereof, in accordance with Newton's laws of motion.
Newton's First Law: Newton's First Law, also known as the Law of Inertia, states that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity, unless acted upon by an unbalanced force. This law establishes the fundamental principle that an object's state of motion will not change unless an external force is applied.
Newton's Second Law: Newton's second law of motion states that the acceleration of an object is directly proportional to the net force acting upon it and inversely proportional to its mass. This law describes the relationship between an object's motion and the forces acting upon it, providing a fundamental principle for understanding the dynamics of physical systems.
Newton's Third Law: Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object exerts an equal and opposite force on the first. This principle of action and reaction forces is fundamental to understanding the dynamics of various physical systems, from collisions to rocket propulsion.
Normal force: The normal force is the perpendicular contact force exerted by a surface on an object resting on it. It counteracts the weight of the object.
Normal Force: The normal force is a contact force that acts perpendicular to the surface of an object in response to an external force pressing the object against the surface. It is a fundamental concept in classical mechanics, particularly in the study of Newton's laws of motion.
Static Equilibrium: Static equilibrium is a state of balance where the net force and net torque acting on an object are both zero, resulting in the object remaining at rest or maintaining a constant velocity. This concept is central to understanding the behavior of objects under the influence of various forces, such as normal, tension, and other examples of forces, as well as the conditions for equilibrium in statics problems.
Tension: Tension is the force exerted by a string, rope, or cable when it is pulled tight by forces acting from opposite ends. It is a contact force that acts along the length of the medium and transmits force between objects.
Tension Force: Tension force is a type of contact force that acts on an object when that object is pulled by one or more forces. It is the force exerted by a string, rope, or cable when it is used to pull an object. Tension force is a vector quantity, meaning it has both magnitude and direction, and it acts in the direction of the pulling force.
W = mg: The equation W = mg, where W represents the weight of an object, m represents the mass of the object, and g represents the acceleration due to gravity, is a fundamental relationship in the context of forces. This equation describes the force of gravity, also known as the weight force, acting on an object.
W_∥: W_∥ represents the work done by a force parallel to the displacement of an object. It is a key concept in understanding the relationships between force, displacement, and work in the context of normal forces, tension, and other examples of forces.
W_⊥: W_⊥ represents the component of the work done by a force that is perpendicular to the displacement of the object. It is an important concept in the context of normal forces, tension, and other examples of forces in physics.
Weight: Weight is the force exerted on an object due to gravity. It is calculated as the product of mass and gravitational acceleration.
Weight: Weight is the force exerted on an object due to gravity, calculated as the product of the object's mass and the acceleration due to gravity. This force is dependent on both the mass of the object and the gravitational field strength where the object is located. Understanding weight is crucial for analyzing motion, forces acting on objects, and buoyancy in fluids.