Physics

• Scalars


  physical quantities that have magnitude but no direction

  
  

  ex. mass, speed

  
• Vectors


  physical quantities with both magnitude and direction

  
  

  ex. force, velocity

  
• Displacement (Δx)


  the change in position that goes in a straight-line path from the initial position to the final position and is independent of the path taken

  
  

  SI unit: m
• Average velocity


  a change in an objects displacement in a given time; it is a vector quantity

  
  

  SI unit: m/s

  
• Acceleration


  the rate of change of an objects velocity; it is a vector quantity

  
  

  SI unit: m/s^2

  
• Linear motion


  Problem solving:

  1. when solving for time (t) there will always be two value for t: time when the projectile is initially launched and time when it hits the ground

  2. to find max height (h): remember that at the max height the vertical velocity (Vy) is 0

  
• Projectile Motion


  Vx = Vsinθ

  Vy = Vcosθ

  
  

  Vo = (Vx,o^2 + Vy,o^2)^(1/2)

  
  

  @ max height: Vy = 0

  
  

  Vx,f = Vo,x (no acceleration in x direction)

  Vy,f = - Vo,y

  
• Frictional Forces


  Static friction (fs): the force that must be overcome to set an object in motion

  
  

  0 </= fs </= usN

  
  

  Kinetic friction (fk): opposes the motion of objects moving relative to one another

  
  

  fk = ukN

  
  

  ***fs is always greater than fk

  
• Frictional Forces graph

  
• Newton's First Law (law of inertia)


  A body in a state of motion or at rest will remain in that state unless acted upon by a net force
• Newton's Second Law


  When a net force is applied to a body of mass m, the body will be accelerated in the same direction as the force applied to the mass

  
  

  F = ma

  
  

  SI unit: N (1 N = 1 kgm/s^2)

  
• Newton's Third Law


  If body A exerts a force on body B, then B will exert a force back onto A that is equal in magnitude but opposite in direction

  
  

  Fb = - Fa

  
• Newton's Law of gravitation


  All forms of matter experience an attractive force to other forms of matter in the universe; the magnitude of the force (Fg) decreases as distance between objects increases

  
• Mass (m)


  a scalar quantity that measures a body's inertia

  
  

  SI unit: kg
• Weight (Fg)


  a vector quantity that measures a body's gravitational attraction to the earth

  
  

  SI unit: N

  
  

  g = -9.8 m/s^2

  
  

  g is the downward vertical acceleration that resulting from the force of gravity

  
• Uniform circular motion


  Centripetal force (Fc) is always perpendicular to velocity and is what maintains circular motion; ac always points inward

  
• First condition of equilibrium

  An object is in translation equilibrium when the sum of the forces acting on it are zero

  
• Terminal velocity (add more info)

  Fdrag (upward) opposes Fg (downward)

  
  

  Fg > Fd: person accelerates downward

  Fg = Fd: terminal velocity is reached (person travels at constant velocity)

  
  

  Net force equals Fd - mg; velocity is proportional to mass of object (heavier objects travel faster)

  
  

  (fact check)

  
• Work


  For a constant force (F) acting on an object that moves a displacement of d, the work (W)

  
  

  W = Fd

  
  

  SI unit: J (Nm)

  
  

  When F is perpendicular to d; W = 0

  
  

  When piston expands; work is done BY the system (W < 0)

  When piston compresses; work is done ON the system (W > 0)

  
  

  The area under a P-V curve is the amount of work done in a system

  
• Compression is work done ____ system and is _______


  on, positive
• Expansion is work done _____ system and is _______

  by, negative
• Power


  the rate at which work is performed

  
  

  P = W/Δt

  
  

  SI unit: W (1 W = J/s)
• Mechanical energy


  Energy is a scalar quantity; total mechanical energy (E) is conserved when the sum of the kinetic and potential energies remains constant

  
  

  E = PE + KE

  
  

  SI unit: J
• Kinetic energy


  the energy associated with moving objects

  
• Potential energy


  the energy associated with a boy's position; gravitation potential energy of an object is due to the force of gravity acting on an object

  
• Work-Energy Theorem


  Relates the work performed by all forces acting on a body in a particular time interval to the change in energy at that time

  
  

  W = ΔE

  
• Conservation of Energy


  When there are no nonconservative forces (such as friction) acting on a system, the total mechanical energy remains constant

  
• Linear expansion


  the increase in length by most solids when heated

  
  

  Mnemonic: when temperature increases, the length of a solid increases "a Lot"

  
• Volume expansion


  the increase in the volume of fluids when heated

  
  

  (β = 3α)

  
• Conduction


  the direct transfer of energy via molecular collisions

  
• Convection


  the transfer of heat by the physical motion of a fluid

  
• Radiation


  the transfer of energy by electromagnetic waves

  
• Specific heat (c)


  Can only be used to find Q when the object is not undergoing a phase change

  
  

  Q > 0 (endothermic): heat is gained

  Q < 0 (exothermic): heat is lost

  
  

  ***specific heat of water 4.18 J/gC or 1 cal/gC

  
  

  Common units: J, cal, Cal (kcal)

  
• Heat of transformation


  the quantity of heat required to change the phase of 1 g of a substance

  
  

  phase change is isothermal (constant temperature)

  
  

  L = latent heat of transformation

  
• First law of thermodynamics

  ΔU = Q - W
• Adiabatic


  Q = O

  
  

  First law becomes: ΔU = - W
• Isochoric


  ΔV = 0 (W = 0)

  
  

  First law becomes: ΔU = Q - W
• Isothermal


  ΔT = 0 (ΔU = 0)

  
  

  Q = W
• Second law of thermodynamics

  In any thermodynamic process that moves from one state of equilibrium to another, the entropy of the system and environment together will either increase of remain unchanged

  
  

  Entropy: ΔS = qL/T

  
  

  SI unit: J/molK

  
• Density (ρ)


  Changes with phase changes for a type of matter

  
  

  SI unit: kg/m^3

  
  

  **Density of water: 10^3 kg/m^3 (1 g/cm^3)

  
  

  1 g/cm^3 = 10^3 kg/m^3