IB Physics

IB Physics

1. Measurements

   • Uncertainties
     • Sum and diference:
       • Sum of the absolute uncertainties
     • Product and Quotient
       • Addition of the percentage uncertainties
     • Powers and roots
       • The product of the exponent and the percentage uncertainty
   • Types of error
     • Systematic: due to system or apparatus
     • Random: due to uncontrollable factors
   • Vectors
     • Physical quantities with magnitude and direction
   • Scalars
     • Physical quantities with only magnitude

2. Mechanics

   • Kinematics
     • Uniform motion
       • linear trajectory and constant velocity
       • Velocity is the rate of change of position
     • Uniformly accelerated motion
       • Acceleration
         • change of velocity per unit time
       • Linear trajectory and constant acceleration
   • Forces and dynamics
     • Force
       • First Law of Newton
         • An object will remain in its state of motion, at rest or with constant velocity, unless and external unbalanced force is applied to it
       • Second Law of Newton
         • The acceleration of an object is inversely proportional to its mass and directly proportional to the net force applied to it
         • The force applied on an object is the rate of change of momentum
           • Momentum = mass times velocity
             • Impulse is the change of momentum or the force applied on an object times the time interval in which it is applied.
             • Conservation of momentum
               • The momentum of an isolated system remains constant
       • Third law of Newton
         • When an object exerts a force on another object, the second object will expert a force equal in magnitude but in opposite direction to the first object
   • Work, energy and power
     • Energy is the ability to do work
       • Work is transfer of Energy
         • Power is the rate at which work is done or rate at which energy is transferded
         • Work = force times the displacement of an object
       • Potential energy = force of gravity times hight of an object
       • Kinetic energy = (1/2)(m)(v^2)
       • Conservation on energy
         • Ideal
           • Energy is not lost by heat to surrounding
         • Not ideal
           • Energy is lost as heat to the surroundings
   • Uniform circular motion
     • Centripetal acceleration: acceleration towards the center
       • Centripetal acceleration = (v^2)/(radius)
         • Centripetal force: sum of all forces towards the center.
     • Angular displacement: Change of angle during a rotation
       • Angular velocity: angular displacement over time
         • Frequency: number of revolutions per unit time
           • Time is the time needed for one revolution

3. Thermal

   • Heat (Q) is the transfer of energy
   • Change of temperature
     • Heat capacity (C) is the energy needed to raise the temperature of an object by 1º C
       • Specific heat capacity (c) is the energy needed to raise the temperature of a material by 1ºC per 1 kg of the material
         • c=(heat)/(mass times change of temperature)
     • Change of phase
       • Latent heat capacity: energy needed to change of phase per unit mass
         • Latent heat of fusion (Lf): energy needed to change from solid to liquid per unit mass
           • Latent heat of evaporation: energy needed to change from liquid to gas per unit mass
       • Evaporation
         • Boiling
           • Happens only at boiling point and in all molecules of the object
         • Happens all the time and only in molecules of the surface

4. Oscillations and waves

   • Simple Harmonic Motion
     • Conditions: Acceleration must be proportional to the displacement from equilibrium position and acceleration is always directed toward equilibrium point
       • When starting at maximum negative, displacement is negative; velocity is positive, but zero; and acceleration is at its maximum.
         • When starting from maximum positive, displacement is positive; velocity is negative and zero; acceleration is at its maximum
       • Characteristics
         • Amplitude: maximum displacement of the object from eq. position; Eq. position: position when the system is at rest; Time period: time it takes for one cycle; Frequency: number of cycles per unit time.
   • Waves: disturbance that propagates through a medium
     • Pulse: when disturbance is just once
       • Traveling wave: continuous disturbance that propagates energy
         • Stationary: static; they do not propagate energy
         • Transversal: Displacement of medium is perpendicular to the propagation of energy
           • Longitudinal: Displacement of medium is parallel to the propagation of energy
             • sound
               • Velocity: around 340 m/s; cannot be polarized; can be difracted in big openings; refraction: more in solids
           • Light
             • Speed = 3x10^8 m/s; can be polarized; can be difracted; can be reflected; can be refracted
     • Characteristics
       • Amplitude: Maximum displacement of the medium from eq. point; period: time for one cycle to pass through a point; frequency: number of cycles that pass through a point per unit time; wavelength: distance bewteen two consecutive crests in phase; wavespeed: speed of propagation of a wave.
       • Properties
         • Reflection
           • When the wave hits a different medium, the wave bounces back
         • Refraction
           • when a wave passes to another medium
         • Difraction
           • When a wave encounters an obstacle

5. Electric current

   • Electric current: amount of charges per unit time
     • Electric potential difference: work done to move a charge from one point to another point per unit charge
       • Electron Volt: Energy needed to move an electron through a p.d. of 1 volt.
       • Energy & Power
         • e.m.f.: Chemical energy converted to electric energy per unit charge
           • p.d.: Electric energy converted to thermal energy per unit charge
             • Power delivered: amount of chemical energy converted to electric energy per unit time
               • Power dissipated: amount of electric energy converted to thermal per unit time
     • Ohm's Law: The electric current through an ohmic conductor is directly proportional to the p.d. across it, remaining temperature and other physical quantities constant.
       • Voltage = Current times resistance
         • Resistance: The ability of an object to opose a flow of current
           • Resistivity: Ability of a material to opose a flow of current
       • Conductors
         • Copper, salty water, grafite, silver, plasma, minerals
       • Insulators
         • Pure water, plastic, dry wood, air
     • Circuits
       • Parallel
         • Equivalent resistance= sum of all resistances in a circuit
           • Voltage = the sum of all voltages
             • Current is equal in all the circuit
       • Series
         • Equivalent resistance= (1) / [(1/r1)+(1/r2)]
           • Voltage is equal in all the circuit
             • Total current = sum of all currents
       • Mixed
         • Form parallel and series circuits from the farthest to closest