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Physics Cheat Sheet (DRAFT) by

Basic physics with brief coverage of some topics.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Repres­ent­ation of motion

Motion Diagram
Dots that are created in evenly spaced intervals. Larger gaps relate to larger velocity.
Positi­on-Time
Straight line represents constant velocity. Larger gradient large velocity.
Free body
Object is repres­ented as a particle with tails repres­enting forces. Tails represent direction and magnitude.

Newton's Laws of motion

1st Law
If the forces are balanced then the object will maintain its current state of motion.
2nd Law
Relati­onship stating net force is equal to the accele­ration times mass. More mass means increased resistance to change in accele­ration.
3rd Law
Forces have action­-re­action pairs which are equal in magnitude but opposite in direction. These forces act on different objects.

Thermal Physics

Heat
Transfer of thermal energy
Temper­ature
The average speed of all of the particles
Heat flow continues until the average kinetic energy of each atom is the same.

Geomet­rical optics

Electr­oma­gnetic waves come in different wavele­ngths. Some within the visible spectrum and some outside of it.
Reflection and transm­ission of waves occur at any change in medium that the waves travel through.
The law of reflection
The angle of incident light is equal to the reflected light
Ray diagrams can be drawn to locate the position of the image
Light bends in relation to the normal when the medium changes.
Fast - Slow - Towards
Slow - Fast - Away
Refractive index and optical density both have an effect on light speed.
The critical angle is when the refracted ray is 90 degrees to the normal. Meaning no light enters the second medium.
 

Vectors vs Scalars

Scalars - Physical quantities with magnitude but no direction. Scalars can be negative. Some examples are temper­ature, speed, energy and time.

Vectors - Physical quantities with both magnitude and direction. Examples include forces, displa­cement, velocity and accele­ration.

Useful equation

Gravity
F=mg
2nd Law
F= ma
Velocity
v= u + at
Displa­cement
v= ut + 1/2 at2
Other
v2=u2+2as
Kinetic energy
KE=1/2mv2
Thermal change
Q=mc(T­2-T1)
Ohm's Law
V=IR
Power
P=VI, P=I2R, P=V2/R
v = final velocity
u = initial velocity
a = accele­ration
g = gravit­ational accele­ration
t = time
P = power
V = Voltage
I = Current
R = Resistance
T = temper­ature
c = heat capacity
s = distance

Waves

Logitu­dinal waves
Contra­ctions caused by pushing and pulling
Transverse waves
Waves caused by up and down motions
Frequency
Number of crests in a given time
Period
Time between two identical points on a wave
Wavelength
Distance between two crests
Speed increases in lower density and higher force mediums
Superp­osition
Sum of the two waves at a specific point
Wavelength multiplied by frequency is equal to speed of the wave
If speed increases frequency stays constant, amplitude
 

Motion

Time
Total time that has passed since t=0
Time interval
Difference between two times
Distance
Movement of object including double backs (Scalar)
Position
Location of an object relative to origin (Vector)
Displa­cement
A change in position (Vector)

Energy

Energy can be transf­erred across system boundaries through work, heat flow, or particle transfer.
Work
External forces cause movement in a system. Positive work causes movement in the same direction.
Initial energy and work must always be equal to final energy.

Methods of heat transfer

Radiation
Transf­erred through collision of particles
Convection
Occurs in fluids and relies on changes of density during heating.
Radiation
Heat travelling in infrared waves that can pass through vacuums.

Electr­icity

Positive charges can attract neutral objects
Voltage
potential difference - work done per unit charge
Ohmic vs non-ohmic
Ohmic resistors have constant resistant irresp­ective to the voltage across.
In series the voltage changes across resistors and bulbs. Current stays constant.
In parallel current splits and voltage stays constant. The more resistance you add in parallel the more current will flow.
Voltage can be calculated by finding the previous voltage and subtra­cting IR of the resistor.