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reference text: Giancoli, Douglas C. Physics. 5th Ed. Ed. Paul F. Corey. Upper Saddle River: Prentice Hall, 1998.

 

PHYSICS EXPLAINED  

 

If you need a general summary of physics, stay here.  Detailed outlines are on the "Physics Outlines" page and my priceless advce is on the "Physics Advice" page.  Simple. 

 

SUMMARY 

MECHANICS

Speed, Displacement, Velocity

 

*SCALARS are basically just normal numbers.  They ahve a MAGNITUDE  (fancy name for number value) but NO DIRECTION; Speed is a scalar.

 

*VECTORS have a MAGNITUDE and a DIRECTION.

 

When adding vectors, break each into their hroizontal and vertical components using sin and cos, then add the horizontal components, and the vertical compenents, so that you have one horizonatal and one vertical componenet.  Then use  a+ b2 + c2  to find the length of the final vector sum.  

 

 An easy way to find the direction is to use the parallelogram rule--connect the vectors tail-to-tail, then make a parallelogram of them by drawing 2 lines parallel to the originals.  The diagonal is the direction.

 

AVERAGE SPEED = total distance / total time= s = d / t

 

if you graph distance vs. time, the slope is distance/ tome, which is speed.

the derivative is slope at a given point  (calculus stuff, but IB seems to like the concept. 

 

DISPLACEMENT is how far something is from the starting point, the shortest line you can draw between a start and end point.

Say you run a lap on a circular track.  Your displacement is zero because you ended where you started.

 

VELOCITY is speed in a given direction;  so it is a Vector.

 

average velocity = displacement / time = v = d/t

 

MOTION EQUATIONS:

acceleration = change in velocity/ time interval

distance equation:  d = vot + ½at²   

                             vf² = vo² + 2ad 

  Force of Friction = (coefficient of friction) (normal force) 

  If something is on an inclined plane, THE NORMAL FORCE IS THE COMPONENT OF THE WEIGHT THAT'S PERPENDICULAR TO THE SLOPE!

 

ENERGY 

Potential energy = mgh

Kinetic energy = ½mv²

Spring PE =  ½kx²   

 

 

THERMO 

Isobaric = constant pressure

Isochoric/isovolumetric = constant volume

Adiabatic = no heat flows in/out of system

Ideal gas law:  PV = nRT

P = absolute pressure

V = volume

n = # of moles

R =   gas constant

T = Kelvin temperature

P1V1/T1 = P2V2/T2

 Work done compressing a gas isobarically = PΔV

 

Calorimetry

no total change in heat (delta Q = 0)

Q + Q = 0

heat gained + heat lost = 0

mcΔt + mL... -(mcΔt + mL...) = 0

 

ELECTRICITY & CIRCUITS

  • F = kQQ/r2
  • E = F/q: the electric field felt on a point charge = the force on the charge/ the charge...
         *** E = kQ/r2
  • V = Ed  :  the potential due to an electric field at a point is the magnitude of the electric field times the distance
  • I = Q/t : current = the amount of charge that flows/time it takes to flow
  • Once a capacitor is fully charged, no more current flows through a circuit
  • Resistors in series: Same current:  Requivalent = R +  R2 + R3...
  • Resistors in parallel Same voltage, and the current divides according to R values.  More current flows down the path of least resistance: 1/Requivalent = 1/R1 + 1/R2 + 1/R3....
     
  • When you connect 2 capacitors, the VOLTAGE spreads out EQUALLY between the capacitors and the charge distributes itself according to capacitance values.
  • Q = CV, where Q is charge, C is capacitance ( a characteristic of the capacitor--WILL NOT CHANGE) and V is voltage.
  •  

    MAGNETISM AND INDUCED STUFF 

    • Know that induced current opposes the change in flux.  Coils don't like changing, so they try to say the way that they were.  So, if you push a magnet straight iinto a coil, the Δ flux = (Δ magnetic field)(Δ area)(cos Θ)         
    • Think of current and magnetic field working like a corkscrew:  To make the cork (magnetic field) go INTO the wine bottle (paper), you have to twist the corkscrew (the current) CLOCKWISE.  To make the magnetic field come OUT of the paper, the current goes COUNTERCLOCKWISE.
    • Remember to think of :
    • 1.  the direction the flux is incresing/decreasing, with respect to the coil, and then

    2.  the induced current will fight change, so use the corkscrew rule to find the direction that it flows in.

           Induced EMF =  (induced current) (resistance) = -(# of loops)(ΔΦ)/(Δt)     

                ΔΦ = change in flux = (ΔB)(ΔA)cosΘ
                ΔB = change in magnetic field
                ΔA = change in area 
             

                *The negative sign reminds you that the induced EMF fights the change in flux

     

     

    Still confused? Email me with a specific question and I would be happy to respond with what help I can. 

     

     

     

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