Forces Concepts
25 concepts · Grades 6-8, 9-12 · 35 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 15 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 measured in newtons.
Mass
The amount of matter in an object; a measure of how much it resists acceleration.
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 stays in motion at constant velocity, unless acted on by a net force.
Newton's Second Law
The acceleration of an object is equal to the net force applied divided by its mass, in the direction of the force.
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 second law.
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 diagram that represents a single object and shows all external forces acting on it as labeled arrows.
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 external forces, total momentum before = total momentum after.
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 no new type of force is created.
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 friction force acting on an object that is already sliding across a surface.
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 of $\mu_s N$ before the object begins to move.
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 momentum is conserved but kinetic energy is not — some energy is lost to heat, sound, or deformation.
Angular Momentum
The rotational equivalent of linear momentum — a measure of how much rotational motion an object has.