forces terms

Term: Newton (N)

Definition: The SI unit of force; 1 N is the force needed to accelerate 1 kg of mass by 1 m/s².

Term: Net force

Definition: The overall force on an object after all forces are combined (taking direction into account).

Term: Balanced forces

Definition: Forces that are equal in size and opposite in direction; net force = 0, so no change in motion.

Term: Unbalanced forces

Definition: Forces that are not equal; net force ≠ 0, so the object’s motion changes (speed and/or direction).

Term: Friction

Definition: A force that opposes motion between two surfaces that are touching.

Term: Static friction

Definition: Friction that keeps an object at rest from starting to move.

Term: Kinetic (sliding) friction

Definition: Friction acting on an object that is already moving.

Term: Air resistance

Definition: A type of friction that acts on objects moving through the air; often opposite the direction of motion.

Term: Gravity

Definition: A force of attraction between objects that have mass; on Earth it pulls objects toward the center of the Earth.

Term: Weight

Definition: The force of gravity on an object; equals mass × gravitational field strength (W = m·g).

Term: Mass

Definition: The amount of matter in an object; does not change with location; measured in kilograms (kg).

Term: Inertia

Definition: An object’s tendency to resist changes in its motion.

Term: Newton’s First Law (Law of Inertia)

Definition: An object at rest stays at rest, and an object in motion stays in motion at constant velocity unless acted on by an unbalanced force.

Term: Newton’s Second Law

Definition: The acceleration of an object depends on the net force and the mass (F = m·a).

Term: Newton’s Third Law

Definition: For every action force, there is an equal and opposite reaction force.

Term: Normal force

Definition: The support force exerted by a surface on an object, acting perpendicular (90°) to the surface.

Term: Applied force

Definition: A force that is put on an object by a person or another object.

Term: Tension force

Definition: A pulling force transmitted through a string, rope, cable, or wire.

Term: Free-body diagram

Definition: A diagram that shows all the forces acting on a single object with arrows.

Term: Acceleration

Definition: The rate at which velocity changes; can be speeding up, slowing down, or changing direction.

Term: Equilibrium

Definition: A state where all forces on an object are balanced; net force = 0 and motion does not change.