Definitions Paper 1 Flashcards
Define the term centre of mass
The point through which all the weight of an object is deemed to act
Define a moment
A force multiplied by the perpendicular distance from the line of action of the force about the pivot
State the principle of moments
For a system to be in equilibrium the total clockwise moment must equal the total anticlockwise moments about the same point
What is the criteria for a system in equilibrium
The resultant force must be 0 and the resultant moment must be 0
Define a couple
A pair of equal forces acting on a body but not along the same line
Define terminal velocity
The maximum velocity attainable by an object as it falls through a fluid
Define the term work done
The force causing a motion multiplied by the distance travelled in the direction of the motion
State hookes law
The extension produced by a force in a wire or spring is directly proportional to the force applied up to the limit of proportionality
Define specific charge
The ratio of the charge of a particle to its mass
Define the term electron volt
One eV is the kinetic energy gained by an electron when accelerated by a potential difference of one volt
Define the term pair production
A process in which a photon of EM radiation ceases to exist, creating a particle and antiparticle in its place
Define the term annihilation
A process in which a particle and antiparticle collide and their masses are converted to energy in the form of a pair of photons of EM radiation
What are strange particles
Particles that are produced through the strong interaction but decay through the weak interaction
Define the term threshold frequency
The minimum frequency of light which causes electrons to be emitted from the surface of a metal
Define the term work function
the minimum energy needed to remove an electron from the surface of a metal
Define the term stopping potential
The minimum PD between two metal plates that prevents photoelectrons with the highest KE from reaching the other plate
Define the term excitation
A process where an electron moves to a higher energy level
Define the term ionisation
A process where an electron gains enough energy to leave the atom
Define electric current
the rate of flow of charge
Define PD
The work done when one coulomb of charge is moved between two points in a circuit
Define electrical resistance
The ratio of the voltage across a component to the current flowing through it
Define the term resistivity
A measure of how easily a material conducts electricity
State Ohms Law
The current flowing through a metallic conductor is directly proportional to the PD applied across it at a constant temperature
What is a superconductor
A material that has zero resistivity below a certain temperature. This critical temperature depends on the material
Define the term electromotive force (emf)
The amount of energy transferred by a cell per unit charge that passes through it
Define the term terminal potential difference
The voltage measured across the terminals of a cell
What is centripetal acceleration
Acceleration which is always perpendicular to the velocity and always acts towards the centre of the circular motion
What is centripetal force
A resultant force that always acts towards the centre of the circular motion
What is damping
An effect where the energy of an oscillations object is transferred to the surroundings decreasing the amplitude of the oscillations
Define angular speed
The angle through which an object moves per unit time
What are the conditions for simple harmonic motion
An objects acceleration is directly proportional to displacement and is in the opposite direction
What are free vibrations
Oscillations where the total energy remains constant. No external force acts on the system and it vibrates at its natural frequency
What is resonance
A case where the driver frequency is equal to the natural frequency of a system causing the amplitude of oscillations to increase drastically due to an additional gain of energy from the driver
