Speed x time 

Vectors

Adding a Vector 

Subtracting a Vector

A physical quantity having some magnitude in a given direction: Velocity, Acceleration, Force 

Adding a Vector- In same direction ADD

e.i.- walk 1 m/s down a down escalator going 1 m/s. Your total speed is 1+1=2 m/s relative to fixed ground

Subtracting a Vector- In opposite direction SUBTRACT 

e.i.- 100 N force to the right and 50 to the left= 100-50 to the right 

Speed in direction of travel 

Speed or direction 

Changes a constant (only constant w/ acceleration) amount per unit time

change in velocity/ change in time

Constant but 0 with velocity 

e.i.

- forward -- speeding up 

- backwards -- slowing down

-  @ right angles to the motion-- change in direction or turning 

A push or pull in a given direction 

Vector- the strength of a push or pull in a given direction.

NET FORCE- every force acting on an object

Unit-- Newton 

Distance

Changes at an increasing rate each second (acceleration)

Changes equal amounts in equal times (velocity) 

Any object falls to earth with same acceleration

g=10 m/s^2,

in absence of air resistance 

e.i.

- constant downward acceleration g= 10 m/s^2

- upward velocity slows down

- downward velocity increases with time. 

an object at rest or with constant velocity, fixed speed is

in a straight line (inertial motion) 

any object undergoes inertial motion unless acted upon

by a net outside force 

Net force on an object causes the acceleration of that

object proportional to net force, inversely proportional to

mass (m)

a= F_net/m 

tendency of object to stay at constant velocity

resistance to change in motion is proportional to mass  

Force of gravity pulling object to earth i s proportional to

its mass. BUT NOT the same as mass!

Force acting on object by another always comes with an

equal and opposite reaction by the first on the other.

two objects touching each other

e.i.- walking or driving a car: you push back against ground, it pushes you forward

e.i- Rocket: hot gas is pushed out of the rocket. rocket propelled forward by push back of gas

force of gravity

magnitude mg, pointing down

W= m g 

m= object mass

g= 10 m/s^2 on surface of earth.

g on moon much smaller. Things weigh 1/6 as much as on earth 

force between two rigid objects at their surfaces

preventing their motion through each other.

rubbing force between two surfaces

e.i: to be at rest, the net force on it has to be zero

mass x velocity 

p=mv

measures how hard it is to stop an object 

cannot change unless object acted upon by outside force

 p = Force applied times time it's applied 

The same can be either large force over short

time (hard collision) or small force over large time

(gentle collision)

Elastic-- bounce--momentum is conserved and KE

Inelastic--stick--momentum is conserved but NOT KE 

Force applied x distance object is moved 

Units of work/energy: 1 Joule = 1 Newton x 1 meter

W= (mg) h or weight x height lifted 

energy stored in position (with respect to a force) require

WORK against a force to gain potential ENERGY 

1/2 mass x speed squared:

W= 1/2 mv^2 

energy stored in a moving object

KE=1/2 mv^2 

= total amount of work put into accelerating it

= total amount of work it can do coming to a stop

KE is amount of "damage" an object can do

Momentum is how hard it is to stop

bullet of 1kg going at 100m/s

energy cannot be created nor destroyed or lost 

if an object is doing no work, and nothing is doing work

on it

its total energy, KE+PE, does not change 

PE lost (as you lose height) = KE gained (as you gain

speed)

to friction is not gained as PE! it goes into heat or 

thermal energy 

Motion of object goes in repeated cycles

number of cycles completed per unit time

1 Hertz (Hz)= 1 cycle/ second

Frequency is 1/ Period

f= 1/ T

driving frequency equals Natural Frequency--frequency at

which an object will

oscillate IF LEFT TO ITSELF

oscillatory disturbances that travel in some medium,

through space. 

sound wave--travels through air 

displacement of medium is perpendicular to direction of

travel of wave

displacement of medium is along the direction of travel of

the wave

frequency as interpreted by ear

double frequency-- raise pitch by--octave 

amplitude squared of displacement of sound wave

change in air pressure detected by ear

how many overtones sound when a musical note is played

IE how many different frequencies combine to make the

note

Two types--- + and - 

Likes repel, opposites attract 

1 Coulomb (standard metric unit of charge) = charge of 

6.25 x 10^18 electrons 

Charge is not created nor destroyed, but transferred by

transmitting electrons from one object to another

electrons move freely inside

transfer electrons by contact with conductor

all electrons bound to atoms

transfer electrons by vigorous rubbing 

transfers charge between insulators

one becomes positively charged

the other negatively charged 

presence of charge near a conductor "induces" charges

inside conductor to travel

opposite charges nearer to outside charge like charges

farther from it. 

contact with large conductor can remove excess charge

from object. 

Earth (if wet) is an excellent ground

force between two charges q1, q2

depends on each charge 

inversely proportional to distance squared between them

"aura" around any charge, its ability to exert force

measures their ability to exert force on other charges  

Force on test charge in field/ charge of test charge 

show direction of E field at any point

spacing gives sense of its strength 

point--away from--positive charge

point--towards--negative charge 

work done to move test charge to a position / its charge

V= PE/q

V measured in Volts (Joules per Coulomb)

maintains  a constant potential across its leads

High potential positively charged, low potential,

negatively charged

change in electric potential across a circuit element

1 Volt= 1 Joule / Coulomb

flow of charge past a given point-- charge flow per unit

time

1 Ampere= 1 Coulomb / second

resistance to current flow thru a resistor measured in

Ohms

bulb filament= high resistor 

wire= low resistance 

Current= Same

Voltage= different

Voltage= Same

Current= different 

1/R= 1/R1 + 1/R2

P= Voltage x Current ( P=VI) (Watts= Volts x Amps)

Presence of magnetic field turns iron objects into magnets

themselves

a straight wire has a magnetic field that circles it in loops

field proportional to current

Field passes through loop and acts like a bar magnet

North pole= field line leave loop 

South pole= where field line enter loop

many wire loops around unmagnetized iron/steel rod. 

Current magnetizes iron

Result is much stronger magnet than that current alone

 an electric current running perpendicular (or partly perpendicular) to magnetic field to feels a force 

perpendicular to field and current

magnetic field DOES NOT WORK 

a change i the magnetic field passing through a wire loop

or coil induces current in the loop

uses magnetic induction to convert

Mechanical energy--Electric energy 

an eletromagnetic whose magnetic field changes creates

AN INDUCED ELECTRIC FIELD in its vicinity 

c= 300,000,000 meters/second= 3x 10 ^ 8 meters/second

30 cm every 1 billionth second

wavelength x frequency= >c 

Instantaneous ? of light is always c

ROY G. BIV

blue has shorter wavelength than red

Both 

Particle like and Wave-liker properties

quantum of light 

light "particle"

short burst of light energy 

h x frequency 

h--planks constant 

blue? more energy than red: X-ray, Gamma-rays very high

energy 

high energy UV photons kick out electrons from metal.

Lower energy light photons can't

proof of particle nature of light

(energy comes in small bundle rather than spread out everywhere like a wave)

light of one specific frequency seen in emission spectra of

an atom

electron emits light, and decays from high energy orbit to low

change in electron energy=hf=photon energy 

Flourescence

glow of some minerals in UV light

electron excited by UV light decays back to low energy in smaller energy steps

resulting photons are visible light 

glow of black body (eg coals, sun, stove burner)

with temperature

average frequency= temperature of body 

when entering a slower medium, light bends "in" 

when entering fast medium, light bends "out"

refraction of light as goes from lighter air to denser.

See sun horizon when it has already passed below

a point where light from an object is made converge to or diverge from, by using laws of reflection or refraction 

blue light is slower than red

it is bent more by refraction

when light hits a surface from inside a dense medium (e.i. from inside water, trying to got to air) an angle > 45 degrees

100% of light is reflected, 9% is transmitted (passes thru) fiber optics

used to focus light 

focal length of lens

image from distant object is inverted (upside down)

image is real

energy of light is focused at focal point

only part of lens is needed to capture whole image

combination of displacements of two or more waves when colliding 

occurs form any type of wave

bright spots occur when constructive interference between light of two slits occurs

Spacing of peaks depends on wavelength 

Red peaks displaced more than blue

interference from many slits 

used as prism. to spread out light of different frequencies

example of thin film interferences 

interferences of reflected light from front surfaces and back 

color depends on which wavelength constructively interferes

direction in which wave is displaced as travels through medium 

absorbs light, lets other through

converts unpolarized light into ?

crossed -- 100% light absorbed 

reflected glare naturally ?