Force and Pressure

Vocabulary practice flashcards covering fundamental concepts, definitions, classifications, units, and instruments related to force and pressure.

Force

A push or pull exerted on an object by an external agent that is capable of changing its state of rest or motion, speed, direction, or shape and size.

Newton ($\text{N}$)

The S.I. unit of force, denoted by the letter '$\text{N}$'.

Dyne

The C.G.S. unit of force.

Direction of Force

The specific direction in which an object or body is pushed or pulled.

Contact Force

A type of force that can act only when two bodies come into direct physical contact with each other.

Muscular Force

A contact force exerted by a human or animal body that requires the physical action of muscles.

Frictional Force

A contact force that opposes the relative motion of an object when two surfaces are in direct contact with each other.

Mechanical Force

A contact force generated by a machine to push or pull an object, such as a crane lifting heavy loads or scissors cutting paper.

Non-contact Force

A force that acts between objects even when they are not in physical contact with each other.

Gravitational Force

A non-contact attractive force by which the Earth pulls every object towards itself, and which every object exerts on every other object.

Weight

The gravitational force with which gravity pulls an object towards the Earth, measurable using an instrument such as a spring balance.

Magnetic Force

A non-contact attractive or repulsive force exerted by a magnet on another magnet or on magnetic substances such as iron, nickel, and cobalt.

Electrostatic Force

A non-contact attractive or repulsive force exerted by charged bodies on each other and on uncharged bodies.

Nuclear Force

The strongest fundamental force, having high strength but acting over a short distance between protons and neutrons to keep the atomic nucleus stable.

Resultant Force

The total effective force produced when two or more forces act simultaneously on a body, producing the same overall effect as a single force.

Balanced Force

A condition occurring when the resultant of all forces acting on a body is zero, keeping the body in equilibrium without changing its motion.

Unbalanced Force

A condition occurring when the resultant of all forces acting on a body is not zero, causing a change in the body's state of rest or motion.

Thrust

The downward perpendicular force acting on a surface, equal in magnitude to the weight of the body exerting it.

Pressure

The perpendicular force (or thrust) acting downward on a surface per unit area ($P = \frac{F}{A}$).

Pascal ($\text{Pa}$)

The S.I. unit of pressure (named after French physicist Blaise Pascal), defined as a force of $1\,\text{N}$ acting normally on a surface area of $1\,\text{m}^2$ ($1\,\text{Pa} = 1\,\text{N/m}^2$).

Hydrostatic Pressure

The pressure exerted by a liquid on the surface or walls of the container in which it is stored due to its weight, which increases with depth and liquid density.

Fluids

A collective term for liquids and gases, which can flow and exert pressure on the walls of containers and submerged objects.

Manometer

A simple pressure gauge consisting of a vertical U-shaped transparent tube partially filled with liquid (water or mercury) used to measure liquid pressure differences.

Atmospheric Pressure

The force per unit area exerted on all surrounding objects by the weight of the mixture of gases composing Earth's atmosphere ($78\%$ nitrogen, $21\%$ oxygen, and $1\%$ other gases).

Bar

A commonly used unit of atmospheric pressure in meteorology, equal to $10^5\,\text{Pascal}$.

Barometer

An instrument designed to measure atmospheric pressure, first constructed by Evangelista Torricelli using a mercury-filled tube.

Torricellian Vacuum

The empty space formed above the mercury column at the sealed top end of an inverted simple mercury barometer.

Standard Atmosphere ($\text{atm}$)

A standard unit of pressure corresponding to the height of a $760\,\text{mm}$ ($75\text{--}76\,\text{cm}$) mercury column at sea level, equal to $1.013 \times 10^5\,\text{N/m}^2$ ($\text{Pa}$).

Drag

A frictional contact force that opposes the relative motion of an object moving through a fluid.

Squashing

A deformation effect of force where an object flattens as compressive force is applied to it from above.