Physics

Conservatives Forces:

are path independent and do not dissipate energy (gravitational, elastic spring, etc)

Work:

the process by which a quantity of energy is moved from one systetm to another

Work in references to gases

if gas expanded, gas did the work

if gas compressed, work was done on the gas

Power:

the rate at which energy is transferred from one system to another

Work-Energy Theorem:

calculates work via adding all the kinetic energies

W = Delta K

Units for Force, Work/Energy, and Power

Newton, Joule, and Watt

What is a vector?

Have both magnitude (an amount), and a direction.

Ex: displacement, velocity, acceleration, and force

What is a scalar?

Have only amount/magnitude

ex: distance, speed, energy, pressure, and mass

Split a vector into X and Y components

Dot Product Formula for scalar

A * B = |A| |B| cos(𝜃)    

Cross Product Formula for vector

A x B = |A| |B| sin (𝜃) 

Explain the Right Hand Rule to find resultants

What are Newton’s Laws:

Torques that generate clockwise rotation are considered _______, while torques that generate counterclockwise rotation are _______.

negative … positive

Conservative forces

are those that are path independent and that do not dissipate energy

Work

the process by which a quantity of energy is moved from one system to another

positive vs. negative work on a gas

Positive work = gas expanded = gas did work
Negative work = gas compressed = work was done on the gas

Power

the rate at which energy is transferred from one system to another

Zeroth Law of Thermodynamics

objects in thermal equilibrium do not cause any net heat transfer/flow across each other.

First Law of Thermodynamics

states that the change in the total internal energy of a system is equal to the amount of energy transferred in the form of heat to the system, minus the amount of energy transferred from the system in the form of work.

(add energy added, substract energy used for work (U = Q - W))

Second Law of Thermodynamics

objects in thermal contact and not in thermal equilibrium will exchange heat energy such that the object with a higher temperature will give off heat energy to the object with a lower temperature until both objects have the same temperature at thermal equilibrium.

Types of Systems (3)

o   Closed: transfers energy, but no matter

o   Isolated: doesn’t transfer anything

o   Open: transfers both

Heat

the process by which a quantity of energy is transferred between two objects as a result of a difference in temperature

Conduction

heat transfer that is done via direct physical contact (pan)

Convection

heat transfer done by gases and liquids (oven)

Radiation

the transfer of energy by electromagnetic waves. Fun fact, can occur thru a vacuum (microwave)

Specific Heat of Water (in calories)

1 cal/g*k

Isothermal

constant temperature, and therefore no change in internal energy

(change in internal energy (delta U) = 0) … meaning Q (heat) = W (work)

Adiabatic

no heat exchange

Q = 0 (no heat) … so delta U = - W

Isovolumetric

no change in volume , and therefore no work accomplished

W = 0 …. so delta U = Q

Isobaric

constant pressure

Density of Water

1 kg/m³

Specific gravity for water

1 atm and 4 Celsius

Pressure Units

1.013x10⁵ Pa = 760 mmHg = 760 torr = 1 atm

Pascal’s Principle

for fluids that are incompressible a change in pressure will be transmitted undiminished to every portion of the fluid and to the walls of the containing vessel

The fundamental Unit of Charge

e = 1.60 x 10^-19 Coulombs

Insulators

will not easily distribute a charge over its surface and will not transfer that charge to another neutral object very well (nonmetals)

Conductors

when given a charge, the charges will distribute approximately evenly upon the surface of the conductor

Proton Field Lines

extend outwards

Electron Field Lines

extend inwards

Electrical potential energy of two like particles

For like particles it increases as they get closer, and for opposite charges it decreases

Equipotential Lines

a line on which the potential at every point is the same. Three-dimensionally speaking, it isn’t an actual line, but rather a sphere. Hence, moving a charge across one of these lines would not need any work, only moving a charge from one line to another would.

(For negative charges, the electric potential energy increases as we “walk” away from a positive charge)

Electric Dipole / Moment

• A dipole = separated + and − charges

• A dipole moment = how strong that separation is + which way it points

• Direction = negative → positive

• Bigger charge or distance = stronger dipole

• In fields → dipoles rotate and align

Ferromagnetic Materials

like paramagnetic materials, they have unpaired electrons and permanent atomic magnetic dipoles that are normally oriented randomly so that the material has no net magnetic dipole. However, unlike paramagnetic materials, they will become strongly magnetized when exposed to a magnetic field

What do moving charges create?

A magnetic field

Right-Hand Rule

Point the thumb in the direction of I and curve fingers around the wire, that will give you the direction of the magnetic field.

Second Right-Hand Rule

First, position your right thumb in the direction of the velocity vector. Then, put your fingers in the direction of the magnetic field lines. Your palm will point in the direction of the force vector for a positive charge, whereas the back of your hand will pint in the direction of the force vector for a negative charge.

What do you need to create a magnetic field vs. an electric field

magnetic field requires a moving charge
electric field requires only a charge

How to create a magnetic force?

one needs an external electric field acting on a charge moving any direction except parallel or antiparallel to the external field

Electromotive force (emf)

not an actual force but rather the potential difference of the voltage source for a circuit, usually a battery

Current

the movement of positive charge thru a conductive material over time

Voltage

a potential difference between two points

Conductivity

the reciprocal of resistance

Capacitor

have the ability to hold a charge at a particular voltage

Capacitance

the magnitude of the charge stored on one plate to the potential difference across the capacitor

Dielectric Material

another way of saying insulation. These materials increase the capacitance of a capacitor by a factor called the dielectric constant (k) …

o   If capacitor is isolated, its voltage will decrease when dielectric material is introduced, and the stored charge will remain constant

o   If the capacitor is in a circuit, its voltage will stay constant b/c it is dictated by the voltage source, and the stored charge will increase

Resistors in Series

o   Are added … and so is the voltage ↓

o   V_s = V₁ + V₂ + ….

Resistors in Parallel

o   (1/R) = (1/R1) + (1/R2) ….

o   Voltage is the same for each resistor in parallel

Capacitors in Series

o   1/C) = (1/C1) + (1/C2) ….

o   Voltage is added just like for resistors in series

Capacitors in Parallel

o   C = C1 + C2 + ….

o   Voltage is the same for each capacitor in parallel

Rules for Voltage in resistors/capacitors

Voltage regardless of resistor/capacitor, in series is added, and in parallel is the same throughout

Transverse wave

wave oscillates perpendicular to the propagation

Longitudinal Wave

Wave oscillates parallel to the propagation

Frequency vs. wavelength vs. period

frequency: the number of waves passing through a fixed point per second
wavelength: length from crest to crest
period: number of seconds per wave (opposite of frequency)

propagation speed

equals the wavelength times the frequency

node

perfectly between a trough and a cresta

antinode

a crest (so the max point from the center of a wave)

Traveling Wave

Imagine a typical wave emitted from a cartoon character’s laser gun … a perpetually traveling wave (has constant amplitude)

Standing Wave

Appears to be fixed at both ends, and so it oscillates up and down, so as to have a maximum amplitude at one point and then it falls to equilibrium and then it just repeats.

Speed of light (c )

3×10⁸ m/s

Visible light goes from

700 nm (red) to 400 nm (violet)

Law of Reflection

angle of incidence equals angle of reflection

In Snell’s Law, where is theta measured from

from the normal … not from the surface of the object reflecting the light

The photoelectric Effect

when a light of a sufficiently high frequency is incident on a metal in a vacuum, the metal atoms emit electrons, as seen above. Recall that the movement of electrons is known as a current

Value of Planck’s constant (h)

6.6×10^-34 J.s

Strong Nuclear Force

provides the adhesive force between the nucleons within the nucleus

Mass Defect

the apparent loss of mass when nucleons come together as some of the mass is converted into energy … that energy is called the binding energy

What are the 4 Fundamental forces in nature from strongest to weakest

(1) Strong Nuclear Force
(2) Electromagnetic Forces
(3) Weak Nuclear Force
(4) Gravity

Fusion Nuclear Reaction

fusion occurs when small nuclei combine to form a larger nucleus, as the name implies. This produces energy and is how the sun functions

Fission Nuclear Force

kinda like the opposite of fusion, it’s when large nucleus splits into smaller nuclei

Alpha Decay

name like so b/c the atom releases an α-particle (He) … remember that Helium has 2 protons and 2 neutrons, so if some atom loses an α-particle it will become the element 2 protons before it and will have the molecular weight -4 of the current atom

Beta Decay

the atom will emit a ß-particle (an electron, ß^-) …. But actually, it can also release a positron (ß⁺), which is a “positive electron” if you will. So, if we emit an electron our new atom will have a (+) charge, and if we emit a positron, it will have a (-)

Gamma Decay

we emit a photon, this is typically denoted by having the original atom that emits the photon have a next to it, so say, X è X … the (X) is just the same atom but with a removed photon

Neutron Decay

Neutron decay is the process by which a free “floating” neutron becomes a proton; when it decays it’ll emit an electron and a neutrino. All that I want you to gather from this is that going from neutron to proton forms an electron … thus if you perform the opposite of this “reaction” we would be losing a proton from the atom, as we make a neutron!

Electron Capture

when the atom captures an inner electron and combines it with a proton to form a neutron, our new atom will be the element before the original, since it’s missing a proton

Positive Controls

are those that ensure a change in the dependent variable when it is expected (something happens as expected)

Negative Controls

ensures no change in the dependent variable when no change is expected, usually related to the placebo effect. (ex. using water to grow a culture of bacteria against another culture that was given say sugar or something; we already expect that giving it water won’t fundamentally make it develop in an unexpected way)

Nothing happens, as expected

Validity is synonimous of

accuracy (picture a target, if you hit it dead on you are accurate)

Reliable is synonimous with

precision (picture a target, you don’t need to hit it dead on in this case, but if you hit the same area consistently you are precise (reliable), but multiple shots in random places are not)

Single-Blind Experiments

either the patient or the assessor may be “blinded” (not told) on certain information to help remove biases

Double-Blind Experiments

both the pt and assessor won’t know some information

Confounding Variable

an outside, unmeasured factor in a study that influences both the dependent (outcome) and independent (predictor) variables, creating a false or distorted relationship between them

Observational Studies

in medicine fit into 3 categories, which examine the connections between exposures and outcomes

Exposure = risk factors

Cohort Studies

we grab 2 groups, one that is connected to an exposure (risk factors, say smoking), and one that isn’t … then we monitor them for a certain amount of time (20 years), and see what happened to them (the outcome)

Cross-Sectional Studies

we look at a single point in time (for example, we look at how many smokers vs. nonsmokers have lung cancer right now)

Case-Control Studies

we start backwards, so we look for people with the expected outcome and track them back to assess what exposures they had contact with

Selection Bias

when we select the wrong ppl for a study, mainly b/c the makeup of our groups won’t match that of the general population

Detection Bias

when we know something already (like for example how hypertension and diabetes is higher in obese individuals, so a doctor might screen obese ppl for those two things a lot more than he would other people) … we detect a general trend and ride it

The FINER Method

o   Assesses the value of a research question on the basis of whether or not it is

Feasible

Interesting

Novel

 Ethical

Relevant

Equipoise

imagine before we finish a research, we learn that one of the treatments is better than the other, it would be unethical to continue the experiment, b/c by not giving the other group the better treatment you are causing harm