Newton's Laws – Force Types and Related Concepts

Vocabulary flashcards covering definitions, formulas, and distinctions for various force types, mass vs. weight, and related physics concepts discussed in the lesson.

Force

A push or pull exerted on an object due to its interaction with another object.

Contact Force

Any force that arises from direct physical contact between two objects (e.g., friction, normal, tension).

Action-at-a-Distance Force

A force that acts on an object without physical contact (e.g., gravity, electrical, magnetic).

Applied Force (F_app)

A force that a person or another object directly exerts on an object, such as pushing a desk.

Gravitational Force / Weight (F_grav)

The attractive force exerted by Earth (or another massive body) on an object; calculated by F = m g.

Normal Force (F_norm)

The support force exerted by a surface perpendicular to an object in contact with it.

Friction Force (F_frict)

Resistive force between two surfaces that opposes relative motion; depends on the surfaces’ nature and normal force.

Static Friction

Friction that prevents motion between two resting surfaces; ranges up to a maximum of μs Fnorm.

Sliding (Kinetic) Friction

Friction acting when one surface slides over another; magnitude μk Fnorm.

Coefficient of Static Friction (μ_s)

Dimensionless constant giving the maximum ratio of static friction to normal force for two surfaces.

Coefficient of Sliding Friction (μ_k)

Dimensionless constant giving the ratio of kinetic friction to normal force; typically less than μ_s.

Air Resistance (F_air)

A special type of friction acting on objects moving through air; opposes motion and grows with speed/surface area.

Tension Force (F_tens)

Force transmitted through a stretched string, rope, or cable; directed along its length, pulling equally on both ends.

Spring Force (F_spring)

Restoring force exerted by a stretched or compressed spring; seeks to return the system to equilibrium.

Hooke’s Law

For an ideal spring, F_spring = −k x, where k is the spring constant and x is the displacement from equilibrium.

Mass

Amount of matter in an object; invariant with location; measured in kilograms (kg).

Weight

The gravitational force on an object; varies with location; measured in Newtons (N); W = m g.

Gravitational Field Strength (g)

Force per unit mass at a location; on Earth ≈ 9.8 N/kg; varies with altitude and planet.

Free-Body Diagram

A diagram showing all external forces acting on an object with vector arrows indicating magnitude and direction.

Net Force

Vector sum of all forces acting on an object; determines acceleration according to Newton’s Second Law (ΣF = m a).