Download 1) Velocity is a vector quantity that has both magnitude and direction

MR. HOLL’S PHYSICS FACTS
MECHANICS
1) Velocity is a vector quantity that has both magnitude and direction.
2) Speed is a scalar quantity that has ONLY magnitude.
3) Distance is a scalar and represents the total ground covered.
4) Displacement is a vector that represents the straight line distance
from where you started to where you finished. (IT CAN BE ZERO)
5) Acceleration of a projectile on EARTH is always 9.8 m
s2
and points
down even at the highest point. The force also points DOWN.
6) Inertia is the same as MASS.
7) The x-direction or horizontal component of the velocity can be found
using cosine (angle). This formula is on the reference table!!!
8) The y-direction or vertical component (up and down) velocity can be
found using sine (angle). This formula is also on the reference
table!!!
9) Projectiles will ALWAYS have a constant x-direction velocity. The ydirection velocity will change because of gravity. (tup = tdown)
10)
The initial y-velocity of a horizontal projectile is ZERO.
11)
The initial x-velocity DOES NOT affect the time it takes a
horizontal projectile to hit the ground.
12)
MASS does not change when on object is moved to another
planet.
13)
Mass is measured in kilograms (kg).
14)
Weight is measured in Newtons (N). It is a force.
15)
Mass to weight multiply by 9.8.
16)
An object’s weight can change when taken to another planet.
Use the formula W = mg . Remember that g is not 9.81 here!!!
17)
Two vectors will produce a maximum when the angle between
them is 0 degrees. (ADD THEM)
18)
Two vectors will produce a minimum when the angle between
them is 180 degrees. (SUBTRACT THEM)
19)
A force can produce equilibrium if it is less than or equal to the
maximum resultant or greater than or equal to the minimum
resultant.
20)
The resultant is the addition of two or more vectors.
21)
Vectors can be added using the head to tail method. Do this by
starting the second vector at the end of the first vector.
22)
Equilibrium means that Fnet = 0 and there is no acceleration.
This can occur when an object is at rest or moving with constant
velocity.
23)
The GRAVITATIONAL force is ONLY a force of attraction and is
inversely proportional to r 2 . ( r  2r, F 1/4F)
24)
For any object moving at constant velocity, the force of friction
is equal to the applied force. (Coefficients of friction can be found on
the reference table)
25)
The force required to start an object moving (static friction) is
greater than the force need to keep it moving at constant velocity
(kinetic friction).
26)
Impulse is equal to the change in momentum and has the
same units. WATCH THE DIRECTION OF THE FORCE!!!
27)
For any force there is an equal and opposite force. The size
and mass of the two items does not have any impact on this.
28)
Power is the rate at which work is done. Units are Watts or
Joules/second.
29)
When an object is lifted and the power or work is being asked,
you must use the objects weight as the force.
30)
Only the VERTICAL DISTANCE matters when an object is lifted
and you are solving for the power or work.
31)
The force applied to a spring with a hanging mass is the weight
of the mass.
32)
The x-term in any spring equation is the amount of
stretch/elongation.
33)
Gravitational Potential energy is the energy possessed by an
object because of its height. (PE = mgh) As h increases, PE increases
34)
Kinetic energy is the energy possessed by an object because of
its velocity. (KE = 1/2mv^2) v  2v , KE  4KE
35)
Mechanical Energy (PE + KE) is always conserved when there is
no friction. (PE + KE = PE + KE)
36)
The work done by friction is referred to as Internal Energy.
37)
When friction occurs, Mechanical Energy decreases and
Internal Energy increases.
38)
Centripetal force and centripetal acceleration always point
towards the center of the circle.
39)
The velocity will always point tangent to the circle for
centripetal motion.
40)
The equilibrant force is equal in magnitude but opposite in
direction to the resultant vector.
41)
Momentum is conserved in ALL explosions and collisions.
42)
For problems involving average force and time, you must use
the impulse formula. (J = Ft =  p)
43)
The slope of a distance versus time graph is velocity.
44)
The slope of a velocity versus time graph is acceleration.
45)
The area under a force versus time graph is impulse.
46)
The area under a velocity versus time graph is displacement.
47)
The slope of a force versus elongation graph is the spring
constant.
48)
FORCE and ACCELERATION both point down at all times for any
type of projectile motion.
49)
Maximum time of flight and height occurs at a launch angle of
90 degrees and maximum range (displacement) occurs at a launch
angle of 45 degrees. As the angle increases from 0 degrees the
height and time of flight increase. Range increases until the angle is
45 degrees.
ELECTRICITY AND MAGNETISM
50)
Wire resistivity’s are found on the reference table. (Nichrome
has the highest and silver has the lowest.
51)
Wire resistance is proportional to the length and inversely
proportional to the Area. (long, skinny wires = large resistance)
52)
Resistivity cannot change!! It is a property of the metal.
53)
Current is the rate of flow of charge.
54)
In a parallel circuit the total resistance MUST be less than the
smallest resistor. Adding resistors makes the total resistance
decrease.
55)
In a series circuit the total resistance increases as resistors are
added to the circuit.
56)
The slope of a voltage versus current graph is the resistance of
the circuit. (THIS NEEDS TO BE A STRAIGHT LINE)
57)
A variable resistor has a resistance that can be changed.
58)
As the voltage applied to a resistor (constant R) increases the
current also increases. As the voltage decreases, current decreases.
59)
Resistance increases as the temperature of the wire increases.
Resistance decreases as the temperature decreases.
60)
When either resistance or voltage changes in a circuit, current
is affected. (use V = IR)
61)
All resistors in series have equal current (I). Also = to total
current.
62)
All resistors in parallel have equal voltage (V). Also = to total
voltage.
63)
An electron and a proton have equal amounts of charge.
(1e = 1.6 E -19 C)
64)
A coulomb is charge, an amp is current [coulomb/sec] and a
volt is potential difference [joule/coulomb]. I = q/t, V = W/q
65)
An eV (electron volt) is a unit of energy ( 1 ev = 1.6E-19 J). The
work done moving 1 electron through a potential difference of 1 volt
is 1 eV. (W=Vq)
66)
When charged spheres touch each other add the charges and
divide by the number of spheres to find the final charge on each sphere.
67)
Electric Fields point in the direction that a POSITIVE particle
would move. Field direction is away from positively charged objects
and towards negatively charged objects. Electrons will move in a
direction OPPOSITE to the electric field.
68)
When an object gains electrons its charge becomes negative.
When an object loses electrons its charge becomes positive.
69)
An object can ONLY gain or lose charge in whole number
multiples of 1.6 E -19 C. Electrons cannot be split!!
70)
Ammeters must be connected in series and voltmeters must
be connected in parallel.
71)
Magnetic fields point from the north to the south outside the
magnet and south to north inside the magnet.
72) Electrostatic force can be repulsive or attractive depending on the
two charges. Electrostatic force and electric field decreases as the
distance increases. Graph:
LIGHT/WAVES
72)All electromagnetic waves originate from accelerating charged
particles.
73) Sound waves are longitudinal and mechanical. Light waves are
transverse and electromagnetic.
74) Light slows down, bends toward the normal and has a shorter
wavelength when it enters a higher (n) value medium. (FAST SOFA) (n values can be found on the reference table) The bigger
the ‘n’ value the SLOWER light will travel in that medium.
75) All angles in wave problems are measured to the normal.
76) Sound waves CANNOT travel in a vacuum or be polarized. Sound
(longitudinal waves) need a medium to travel through. The speed
of sound can be found on the reference table (331 m/s)
77) The electromagnetic spectrum (electrical, radio, microwaves,
infrared, visible, ultraviolet x-ray and gamma or ERMI VUX G) are
listed lowest energy/lowest frequency, highest wavelength to
highest frequency/energy, lowest wavelength. (The
electromagnetic spectrum is on the reference table)
78) The amplitude of a sound wave determines its energy and
loudness. The amplitude of a light wave determines its brightness.
79) The speed of ALL types of electromagnetic waves (light waves) is
3.0 x 108 m/sec in a vacuum.
80) FAST – SOFA refers to the refraction of light waves when they
travel from one medium to another. (Fast To Slow Towards, Slow to
Fast Away)
81) The keywords for any question involving resonance are
VIBRATIONS and NATURAL FREQUENCY!!
82) Constructive interference occurs when 2 waves meet crest to crest
or trough to trough. ADD the amplitudes and get brighter light or
louder noise!! (0 degree phase difference or whole number
wavelengths apart)
83) Destructive interference occurs when 2 waves meet crest to
trough. SUBTRACT the amplitudes and get dimmer light or softer
noise!! (180 degree phase difference or ½ wavelengths apart)
84) Diffraction effects are greatest for a LONG wavelength and a
SMALL opening.
85) Two points are in-phase if they have the same displacement and
direction of motion and are separated by a whole number of
wavelengths. They are out of phase if they have opposite
displacement and opposite directions of motion.
86) Period is inversely proportional to frequency. As period increases,
frequency decreases. ( T = 1/f) The product of period and
frequency is 1.
87) Period, velocity and wavelength are directly proportional to one
another. If the period doubles, or the velocity doubles the
wavelength also doubles.
88) When a wave travels from one medium to another, some of the
wave is refracted and some of it is reflected. When a wave refracts
there is a change in velocity and direction. (Note: if the wave is on
the normal line it will NOT change directions.)
89) At the critical angle a wave will be refracted to 90 degrees.
90) Wave behavior of light and small particles (electrons) are proven
by diffraction, interference and the polarization.
91) Transverse wave particles vibrate back and forth perpendicular to
the wave direction.
92) Longitudinal wave particles vibrate back and forth parallel to the
wave direction.
93) Diffuse (scattered) reflection occurs from dull or rough surfaces
while regular reflection occurs from mirror (smooth) type surfaces.
94) According to the Doppler Effect, if a wave producing source is
moving towards you, you will experience waves with a HIGHER
frequency and a shorter wavelength. Also remember Red Run
Away, Blue Come and Play.
95) In order for a standing wave to be produced there must be two (2)
waves traveling in opposite directions that have the same
amplitude and frequency.
96) Period is defined as the time for ONE cycle or wavelength.
97) When 2 waves interfere with one another they will continue on
with their original size and direction after the interference occurs.
MODERN PHYSICS
98) Light exhibits both WAVE and PARTICLE properties.
99) Diffraction and interference prove wave properties and momentum
and the photoelectric effect prove particle properties.
100)
Particles (electrons) can exhibit WAVE characteristics.
101) Photons have both energy and momentum!! (E = hf = hc/  )
Energy is proportional to frequency and inversely proportional to
the wavelength.
102) A photon is ABSORBED when an electron moves up an energy
level and a photon is EMITTED when an electron moves down an
energy level.
103) In order for an electron to change energy levels, the photon
MUST have an energy that is equal to the difference between any 2
energy levels.
104) In order to ionize an atom, the photon MUST have the
ionization energy. If it has less than the ionization energy nothing
will happen.
105)
Lost mass gets converted into energy. Formula: E  mc 2
106) 1 universal mass unit (1 u) is equal to 9.31 E 2 MeV. Convert u
to MeV
107) When a particle is annihilated ALL of its mass is converted into
energy.
108) The strong nuclear force holds protons and neutrons (aka
nucleons) together. It is a force of attraction!! It is the strongest
force in the universe and it acts over a very short range.
109) The electrostatic force holds protons and electrons together
because they have opposite charges.
110)
Protons and neutrons are examples of baryons.