Physics Definition Reviewer: Chapters 1 — 5

This set of vocabulary flashcards covers key concepts in physics from chapters including vectors, motion, Newton's laws, friction, energy, and momentum, based on the provided lecture transcript.

Scalar quantity

A physical quantity that has magnitude only and is completely specified by a number and a unit.

Vector quantity

A physical quantity that has both magnitude and direction.

Vector

A way of representing a vector quantity, commonly by an arrow whose length represents magnitude and whose direction shows the direction of the quantity.

Resultant

The single vector that represents the combined effect of two or more vectors.

Right triangle

A triangle that has two sides perpendicular to each other and one right angle of $90^\circ$.

Hypotenuse

The side of a right triangle opposite the right angle; it is always the longest side.

Inverse of trigonometric function

A function used to find an angle when the value of a trigonometric ratio is known, such as arcsin, arccos, or arctan.

Pythagorean theorem

A relationship in a right triangle stating that the sum of the squares of the two shorter sides equals the square of the hypotenuse.

Resolving the vector

The process of replacing one vector with two or more vectors whose combined effect is equivalent to the original vector.

Components of the vector

The individual vectors obtained when a vector is resolved, usually into perpendicular directions such as horizontal and vertical components.

Law of sine and cosine

Trigonometric relationships used to determine unknown sides or angles in triangles, especially non-right triangles.

Velocity

A vector quantity that describes both how fast a body is moving and the direction in which it is headed.

Average velocity

The distance or displacement covered divided by the time taken over the interval considered.

Instantaneous velocity

The velocity of a body at a particular moment or instant.

Delta ($\Delta$)

The Greek letter delta, used to represent a change in a quantity, such as a change in position or velocity.

Constant velocity

Velocity that does not change in magnitude or direction.

Acceleration

The rate at which velocity changes with time; velocity may increase, decrease, or change direction.

Deceleration

A decrease in velocity, corresponding to negative acceleration in the treatment used in the text.

Gravitational acceleration

The downward acceleration experienced by freely falling bodies near Earth’s surface, about $9.8\,m/s^2$ or $32\,ft/s^2$.

Terminal velocity

The limiting velocity reached by a falling body when air resistance prevents it from falling faster.

Falling body

A body moving downward under gravity; when air resistance and buoyancy are neglected, it has the constant acceleration $g$.

Projectile motion

Motion of a launched object in which horizontal and vertical motion are analyzed separately; with air resistance neglected, horizontal velocity remains constant while gravity affects the vertical motion.

Newton’s First Law of Motion

If no net force acts on a body, a body at rest remains at rest and a body in motion remains in motion at constant velocity.

Force

An influence that can change the velocity of a body.

Net force

The vector sum of all the forces acting on a body. A nonzero net force produces acceleration.

Unbalanced force

A force situation in which the forces do not cancel, so the net force is not zero and the body’s velocity changes.

Inertia

The property of a body that resists a change in its state of rest or uniform motion.

Mass

A quantitative measure of inertia; the greater the mass, the less acceleration a body has for a given force.

Kilogram (kg)

The SI unit of mass.

Newton’s Second Law of Motion

The net force acting on a body equals the product of its mass and acceleration, and the acceleration is in the direction of the net force.

Weight

The gravitational force with which Earth attracts a body; near Earth, it equals mass multiplied by gravitational acceleration.

Slug

The British-system unit of mass; a net force of $1\,pound$ acting on $1\,slug$ produces an acceleration of $1\,ft/s^2$.

Pound (lb)

The British-system unit of force.

Free-body diagram

A vector diagram that shows all the forces acting on the body being studied.

Cable

A general term for strings, ropes, or chains that transmit a force; a cable can exert a force through a pulley without changing its magnitude.

Tension

The magnitude of the force that a cable exerts on an attached body; for a light cable, the tension has the same magnitude throughout the cable.

Newton’s Third Law of Motion

When one body exerts a force on another body, the second body exerts an equal force in the opposite direction on the first body; the forces act on different bodies.

Action force

The force one body exerts on another body in an action–reaction pair.

Reaction force

The equal and opposite force exerted by the second body on the first in an action–reaction pair.

Static friction

Friction between surfaces that are at rest relative to each other; it acts to prevent relative motion and can increase up to a maximum value.

Starting friction

The maximum static friction that must be overcome for motion between two surfaces to begin.

Kinetic friction

Friction that acts after relative motion between surfaces has begun; it is generally less than the starting friction.

Sliding friction

Another name used for kinetic friction, acting when surfaces slide relative to each other.

Coefficient of friction

A quantity that describes the frictional interaction between two surfaces; the frictional force is related to the coefficient and the normal force.

Work

A measure of the change produced by a force acting on a body; when force and displacement are in the same direction, work equals force times distance.

Joule (J)

The SI unit of work and energy; one joule is one newton-meter.

Watt (W)

The SI unit of power; one watt is one joule per second.

Energy

A property of something that enables it to do work.

Kinetic energy

The energy a body has by virtue of its motion.

Potential energy

The energy a body has by virtue of its position.

Horsepower (hp)

A unit of power; one horsepower is approximately $746\,watts$.

Foot-pound ($ft \cdot lb$)

A unit of work or energy in the British system, equal to the work done by a one-pound force acting through one foot in the same direction.

Power

The rate at which work is done.

Law of conservation of energy

The principle that energy cannot be created or destroyed, although it can be transformed from one form to another; the total energy remains constant.

Linear momentum

The momentum of a body in straight-line motion, equal to the product of its mass and velocity; its direction is the same as the direction of motion.

Impulse

The product of a force and the time interval during which it acts; impulse equals the change in momentum.

Momentum

The product of a body’s mass and velocity.

Newton-second ($N \cdot s$)

A unit of impulse, equal to a newton of force acting for one second.

Pound-second ($lb \cdot s$)

A British-system unit of impulse, equal to a pound of force acting for one second.

Law of conservation of linear momentum

When the vector sum of external forces on a system is zero, the total linear momentum of the system remains constant, even though momentum may be redistributed among its bodies.

Distribution

The redistribution of total momentum among the different bodies in a system during an interaction.

Collision

An interaction in which moving bodies strike or act on one another and momentum is conserved when external forces are negligible.

Elastic collision

A collision in which both momentum and kinetic energy are conserved.