Forces Concepts
30 concepts · Grades 6-8, 9-12 · 45 prerequisite connections
Forces explain why objects change their motion. Newton's three laws form the backbone: inertia tells us objects resist change, F = ma connects force to acceleration, and action-reaction pairs explain interactions between objects. This family is the largest in physics because forces appear everywhere — friction slowing a sliding box, tension in a tug-of-war rope, gravity pulling a skydiver, or the centripetal force keeping a car on a curved road. Mastering free body diagrams and equilibrium here unlocks momentum, collisions, and rotational physics.
This family view narrows the full physics map to one connected cluster. Read it from left to right: earlier nodes support later ones, and dense middle sections usually mark the concepts that hold the largest share of future work together.
Use the graph to plan review, then use the full concept list below to open precise pages for definitions, examples, formulas, and related guides.
Concept Dependency Graph
Concepts flow left to right, from foundational to advanced. Hover to highlight connections. Click any concept to learn more.
Connected Families
Forces concepts have 18 connections to other families.
All Forces Concepts
Force
A push or pull interaction between two objects that can cause a change in an object's velocity (speed or direction), described as a vector quantity.
Mass
The amount of matter in an object and a fundamental measure of how much it resists changes to its state of motion (inertia).
Weight
The gravitational force acting on an object due to its mass, directed toward the center of a massive body.
Newton's First Law
An object at rest stays at rest, and an object in motion continues moving at constant velocity in a straight line, unless acted upon by.
Newton's Second Law
The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass, with the acceleration pointing.
Newton's Third Law
For every action force, there is an equal in magnitude and opposite in direction reaction force.
Inertia
The intrinsic tendency of an object to resist any change in its state of motion, whether at rest or moving.
Friction
A contact force that opposes the relative motion or tendency of motion between two surfaces in contact.
Normal Force
The perpendicular contact force that a surface exerts on an object pressing against it, directed away from the surface.
Gravity
The universal attractive force between any two objects with mass, decreasing with the square of distance.
Net Force
The single resultant force obtained by vector addition of all individual forces acting on an object, which alone determines the object's acceleration according to Newton's.
Equilibrium
A state in which all forces acting on an object balance so that the net force equals zero and there is no acceleration.
Tension
The pulling force transmitted through a rope, string, or cable when it is pulled taut at both ends.
Free Body Diagram
A simplified diagram that isolates a single object and represents all external forces acting on it as labelled arrows originating from the object's centre of.
Momentum
The product of an object's mass and velocity, representing the quantity of motion it carries.
Impulse
The product of force and time interval, equal to the resulting change in an object's momentum.
Conservation of Momentum
In a closed system with no net external force, the total momentum of all objects remains constant before and after any interaction — momentum is.
Centripetal Force
The net inward force required to keep an object moving along a circular path, directed toward the centre of the circle, equal to $mv^2/r$ where.
Torque
The rotational equivalent of force; a measure of how much a force tends to cause an object to rotate about an axis.
Spring Force
The restoring force exerted by a spring, proportional to how much it's stretched or compressed.
Kinetic Friction
The constant friction force acting on an object that is already sliding across a surface, equal to the product of the coefficient of kinetic friction.
Static Friction
The friction force that prevents a stationary object from beginning to slide when an external force is applied, adjusting in magnitude up to a maximum.
Elastic Collision
A collision in which both the total momentum and the total kinetic energy of the system are fully conserved after impact.
Inelastic Collision
A collision in which the total momentum of the system is conserved but the total kinetic energy is not — some kinetic energy is converted.
Angular Momentum
The rotational equivalent of linear momentum, measuring the quantity of rotational motion in a spinning or orbiting object.
Statics
Statics is the study of objects in equilibrium, where the net force and net torque are both zero.
Pulley Systems
Pulley systems are arrangements of ropes and wheels used to change the direction of a force or to gain mechanical advantage.
Collisions
A collision is an interaction in which objects exert large forces on each other for a short time, changing their momenta.
Rotational Equilibrium
Rotational equilibrium is the condition in which the net torque on an object is zero, so its angular velocity does not change.
Orbital Motion
Orbital motion happens when gravity continuously pulls an object inward while the object keeps moving forward, producing a curved path around a planet, moon, or.