Unit 1 Definitions

Homogenous

Correct in terms of units

Scalar

Has magnitude only

Vector

Has both magnitude and direction

Density

Mass per unit volume

Newton’s First Law

An object remains stationery or at uniform motion unless acted upon an external unbalanced force

Newton’s 2nd Law

The rate of change of momentum is directly proportional to the resultant force acting upon it

Moments

Turning effect around a pivot

Principle of Moments

States that when an object is in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments

Centre Of Gravity

Single point of a body in which the entire weight of the body can be considered to act

Stability

A measure of how far an object can tilt before toppling over

Two conditions for equilibrium

No net force
No net moment

Displacement

Shortest path from A to B, with direction

Speed

The rate of change of direction

Velocity

Rate of change of displacement

Acceleration

Rate of change of velocity

Dynamics

The study of the causes of and changes to motion

Newton’s Third Law

When body A exerts a force on body B, body B exerts an equal but opposite force on body A

Conditions of Newton’s 3rd Law Pair

Forces are equal and opposite
Same type of forces
Two objects are involved

Momentum

Measure of how difficult something is to stop

Principle of Conservation of Momentum

The total momentum, in a closed system, before an interaction is equal to the total momentum after, given no external forces act

Elastic Collision

Collision where momentum and kinetic energy is conserved

Inelastic Collision

Collision where momentum is conserved but KE isn’t

Principle of Conservation of Energy

States that energy cannot be created nor destroyed, but only be transferred from one form to another

Work

Done when a force causes an object to move

Moment of a force about a point

The force multiplied with the perpendicular distance between the line of motion of action of the force and pivot

Power

The rate of doing work or the rate of energy transfer

Hadrons

Particles consisting of quarks or antiquarks that interact through the strong force

Leptons

Electrons and electron neutrinos, that are fundamental

Fundamental

Cannot be broken apart

Mesons

Hadrons made of a quark and anti-quark pair

Baryons

Hadrons made up of three quarks

Nucleus

The centre of an atom, where protons and neutrons live

Isotope

An atom of an elements with the number of protons, but different number of neutrons

Conservation of Charge

The total charge after the reaction is always equal to the total charge before

Conservation of Baryon Number

The total baryon number after the reaction must be equal to the total baryon before the reaction

Conservation of Lepton Number

The total lepton number after the reaction must be equal to the total lepton before the reaction

Strong force Indicators

Only hadrons involved

Weak Force Indicators

Electron neutrino involved
Quark flavour change

Electromagnetic Force Indicators

Gamma photon produced
Repulsion