Physics Definitions - Grade 12
Newton's first law - An object continues in its state of rest or uniform velocity unless it is acted on by a
net or resultant force.
Newton's second law - When a net force is applied to an object, it causes the object to accelerate in the
direction of the net force.
Acceleration is directly proportional to net force
Acceleration is inversely proportional to mass
Newton’s third law - If object exerts A exerts a force on object B, then object B will simultaneously exert
an opposing force that is equal in magnitude on object A
1 - continue 2 - accelerate 3 - oppose
Electric field - a region of space around a charged particle in which a point charge would experience a
force.
EF strength - the force experienced per unit positive charge
GF strength - the force experienced per unit mass
EMF - the total energy supplied per coulomb of charge by the cell
Potential difference - work done per unit positive charge
Weight has direction - A measure of the force between Earth and an object near its surface.
Momentum - The product of the mass and the velocity of an object.
p=mv Δp=m(vf-vi) [Kg.m.s-1]
NII in terms of momentum - The net force acting on an object is equal to the rate of change of
momentum. Fnet=Δp/Δt
An isolated system - is one that has no net external forces acting on it
Conservation of momentum - The total linear momentum of an isolated system remains constant.
Pbefore = Pafter [m1v1 + m2v2 = m1v3 + m2v4]
Elastic collision - a collision where momentum and kinetic energy are conserved
Inelastic collision - a collision where only momentum is conserved.
Prove: KEbefore = KEafter [1/2mv2 + 1/2mv2 = 1/2mv2 + 1/2mv2]
Impulse - The product of the net force and the contact time of the net force.
Area under force time graph
J=Fnet.Δt (= Δp) [N.s]
Fleming's left hand motor rule (the motor effect) - A current-carrying conductor can experience a force
when placed in a magnetic field. (Electrical energy to mechanical energy)
F=BIcosθ [T (Tesla)] [inc: I, B, turns, current]
Induction - When there is a change in the magnetic flux linkage with a conductor, a potential difference
is induced.
Magnetic flux - the product of the magnetic field and the area through which the magnetic field lines
pass.
Φ=BAcosθ [Wb (Webers)] [θ=normal to coil] [linkage = Φ x Number of turns of wire]
Lenz’s law - The induced current Flows in such a direction as to set up a magnetic field to oppose the
change in magnetic flux.
Generator - Right hand dynamo rule (Mechanical energy to electrical energy)
DC - split-ring commutator AC - slip rings
Transformer - Uses mutual induction to alter the voltage of an appliance.
Ns/Np = Vs/Vp [Ns = Number of turns secondary Vp = Voltage primary] [VpIp = VsIs] [W=I2Rt]
Newton's first law - An object continues in its state of rest or uniform velocity unless it is acted on by a
net or resultant force.
Newton's second law - When a net force is applied to an object, it causes the object to accelerate in the
direction of the net force.
Acceleration is directly proportional to net force
Acceleration is inversely proportional to mass
Newton’s third law - If object exerts A exerts a force on object B, then object B will simultaneously exert
an opposing force that is equal in magnitude on object A
1 - continue 2 - accelerate 3 - oppose
Electric field - a region of space around a charged particle in which a point charge would experience a
force.
EF strength - the force experienced per unit positive charge
GF strength - the force experienced per unit mass
EMF - the total energy supplied per coulomb of charge by the cell
Potential difference - work done per unit positive charge
Weight has direction - A measure of the force between Earth and an object near its surface.
Momentum - The product of the mass and the velocity of an object.
p=mv Δp=m(vf-vi) [Kg.m.s-1]
NII in terms of momentum - The net force acting on an object is equal to the rate of change of
momentum. Fnet=Δp/Δt
An isolated system - is one that has no net external forces acting on it
Conservation of momentum - The total linear momentum of an isolated system remains constant.
Pbefore = Pafter [m1v1 + m2v2 = m1v3 + m2v4]
Elastic collision - a collision where momentum and kinetic energy are conserved
Inelastic collision - a collision where only momentum is conserved.
Prove: KEbefore = KEafter [1/2mv2 + 1/2mv2 = 1/2mv2 + 1/2mv2]
Impulse - The product of the net force and the contact time of the net force.
Area under force time graph
J=Fnet.Δt (= Δp) [N.s]
Fleming's left hand motor rule (the motor effect) - A current-carrying conductor can experience a force
when placed in a magnetic field. (Electrical energy to mechanical energy)
F=BIcosθ [T (Tesla)] [inc: I, B, turns, current]
Induction - When there is a change in the magnetic flux linkage with a conductor, a potential difference
is induced.
Magnetic flux - the product of the magnetic field and the area through which the magnetic field lines
pass.
Φ=BAcosθ [Wb (Webers)] [θ=normal to coil] [linkage = Φ x Number of turns of wire]
Lenz’s law - The induced current Flows in such a direction as to set up a magnetic field to oppose the
change in magnetic flux.
Generator - Right hand dynamo rule (Mechanical energy to electrical energy)
DC - split-ring commutator AC - slip rings
Transformer - Uses mutual induction to alter the voltage of an appliance.
Ns/Np = Vs/Vp [Ns = Number of turns secondary Vp = Voltage primary] [VpIp = VsIs] [W=I2Rt]
