PHYSICS DEFINITIONS
Kinematics
• Define a vector as a physical quantity that has both magnitude and direction and give examples
• Define a scalar quantity as a physical quantity that has magnitude only and give examples
• Define resultant vector as the single vector which has the same effect as the original vectors acting
together
• Define distance as the length of path travelled and know that distance is a scalar quantity
• Define displacement as a change in position
• Define speed as the rate of change of distance and know that speed is a scalar quantity
• Define velocity as the rate of change of position or the rate of displacement or the rate of change of
displacement and know that velocity is a vector quantity
• Define acceleration as the rate of change of velocity
Newtons Laws and Application of Newtons laws
• Define weight Fg as the gravitational force the Earth exerts on any object on or near its surface
• Define normal force, FN, as the perpendicular force exerted by a surface on an object in contact
with it
• Define frictional force due to a surface, Ff, as the force that opposes the motion of an object and
acts parallel to the surface with which the object is in contact
• State Newton's first law: An object continues in a state of rest or uniform (moving with constant)
velocity unless it is acted upon by a net or resultant force
• Define inertia as the property of an object that causes it to resist a change in its state of rest or
uniform motion
• State Newton's second law: When a net force, Fnet, is applied to an object of mass, m, it
accelerates in the direction of the net force. The acceleration, a, is directly proportional to the net
force and inversely proportional to the mass
• State Newton's third law: When object A exerts a force on object B, object B simultaneously
exerts an oppositely directed force of equal magnitude on object A
Momentum, Impulse, Work, Energy and Power
• Define linear momentum as the product of the mass and velocity of the object
• State Newton's second law in terms of momentum: The net force acting on an object is equal to the
rate of change of momentum. (Note: there are two acceptable statements of Newton's Second
Law)
• State the law of conservation of linear momentum: The total linear momentum of an isolated
system remains constant (is conserved)
• Define an elastic collision as a collision in which both momentum and kinetic energy are conserved
• Define an inelastic collision as a collision in which only momentum is conserved
• Define impulse (J) as the product of the net force and the contact time
• Define the work done on an object by a force as the product of the displacement and the
component of the force parallel to the displacement
• Define gravitational potential energy as the energy an object possesses due to its position relative
to a reference point
• Define kinetic energy as the energy an object has as a result of the object's motion
• Define mechanical energy as the sum of gravitational potential and kinetic energy at a point
• State the law of conservation of energy as the total energy in a system cannot be created nor
destroyed; only transformed from one form to another
• State the principle of conservation of mechanical energy: In the absence of air resistance or any
external forces, the mechanical energy of an object is constant
• The Work-Energy theorem: The work done by a net force on an object is equal to the change in the
kinetic energy of the object.
• Define power as the rate at which work is done or the rate at which energy is transferred
• State that the unit of power is the watt (W). One watt is defined as the power when one joule of
work is done in one second. (1 W = 1 J·s−1)
• Define efficiency as the ratio of output power to input power
Gravitational and Electrical Fields
• State Newton's Law of Universal Gravitation: Every particle with mass in the universe attracts every
other particle with a force which is directly proportional to the product of their masses and
inversely proportional to the square of the distance between their centres
• Define weight (Fg) as the gravitational force the Earth exerts on any object on or near its surface
• Define gravitational field as the force acting per unit mass
• State Coulomb's law in words: Two point charges in free space or air exert forces on each other.
The force is directly proportional to the product of the charges and inversely proportional to the
square of the distance between the charges
• Define the magnitude of the electric field at a point as the force per unit positive charge E = F/q
where E and F are vectors
Electric Circuits
• Define potential difference as the work done per unit positive charge V = W/Q
• Define current as the rate of flow of charge I = q/t
• State Ohm's Law: Current through a conductor is directly proportional to the potential difference
across the conductor at constant temperature
• Define resistance as a material's opposition to the flow of electric current
• Define emf as the total energy supplied per coulomb of charge by the cell
Electrodynamics
• Define magnetic flux linkage as the product of the number of turns on the coil and the flux through
the coil (NФ)
• State Faraday's law of electromagnetic induction: the emf induced is directly proportional to the rate
of change of magnetic flux (flux linkage)
• State Lenz's law: the induced current flows in a direction so as to set up a magnetic field to oppose
the change in magnetic flux
• Define a diode as a component that only allows current to flow in one direction
Photons and Electrons
• Define threshold (cut-off) frequency (fo) as the minimum frequency of incident radiation at which
electrons will be emitted from a particular metal
• Define work function (Wo) as the minimum amount of energy needed to emit an electron from the
surface of a metal
