Forces, Newton’s Laws & Circular Motion – Vocabulary

Vocabulary flashcards covering the fundamental terms introduced in the July 7–14 physics lectures on forces, Newton’s laws, free-body diagrams, friction, constraint systems, circular motion, and gravitation.

Force

A push or pull exerted on an object that can cause it to accelerate; measured in newtons (N).

Net Force

The vector sum of all forces acting on an object; determines the object’s acceleration by F = ma.

Newton’s First Law (Law of Inertia)

An object remains at rest or moves with constant velocity unless acted on by a net external force.

Newton’s Second Law

The acceleration of an object is proportional to the net force acting on it and inversely proportional to its mass (F = ma).

Newton’s Third Law

For every action force there is an equal and opposite reaction force acting on a different object.

Free-Body Diagram (FBD)

A sketch showing all external forces acting on an isolated object, represented as vectors from the object’s center of mass.

Equilibrium

State in which the net force on an object is zero, resulting in zero acceleration (object at rest or constant velocity).

Weight

The gravitational force exerted on an object’s mass by Earth; W = mg.

Apparent Weight

The normal force a surface (or scale) exerts on an object; changes when the object accelerates (e.g., in an elevator).

Friction Force

A resistive force parallel to a surface that opposes relative motion or attempted motion between surfaces.

Static Friction

Friction that prevents relative motion up to a maximum value; Fs,max = μs N.

Kinetic Friction

Friction acting when two surfaces slide relative to one another; magnitude Fk = μk N.

Normal Force

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

Tension

The pulling force transmitted through a string, rope, or cable when it is taut.

Constraint System

A collection of objects whose motions are linked (e.g., blocks connected by ropes and pulleys) so that their accelerations are related.

Rope & Pulley System

Mechanical arrangement using massless ropes and frictionless pulleys to transmit tension and relate object accelerations.

Spring Scale

A device that measures force (often calibrated in newtons or apparent mass) via the extension of an internal spring.

Uniform Circular Motion

Motion in a circle at constant speed where velocity’s direction changes continuously, producing centripetal acceleration.

Centripetal Acceleration

Acceleration directed toward the center of a circular path; magnitude a = v²/r.

Centripetal Force (Not a new force)

Name given to the net inward force required for circular motion; provided by real forces such as tension, gravity, friction, or normal force.

Circular Motion Apparent Weight

The normal force felt by an object in circular motion, differing from true weight due to centripetal requirements.

Banked Curve

An inclined roadway or track that uses the horizontal component of normal force (and possibly friction) to provide centripetal force for a turning vehicle.

Orbiting Object

Body in free-fall around a central mass; its period and orbital radius obey Newton’s law of gravity.

Newton’s Law of Universal Gravitation

Every two masses attract each other with force F = G m₁m₂/r², acting along the line connecting their centers.

Bi-Modal Grade Distribution

Assessment outcome in which scores cluster around two distinct performance levels, as noted in the midterm recap.