Exemption Exam PhyS 100 BYU

4 Ways to Gain Knowledge

RISA

1. Reason

2. Intuition

3. Sensory Data

4. Authority

6 Self Evident Truths

TEPNOC

1. Time Symmetry

2. Existence

3. Position Symmetry

4. Non-contradiction

5. Occam's Razor

6. Causality

Existence

ex.

A driver tells his insurance company that a dent in his car was caused by an accident he was in. The insurance company learns that the dent existed before the accident and was in a different part of the car from where the accident occurred.

Time Symmetry

ex.

A geologist estimates the age of a river valley by assuming the same laws governing the erosion process she sees occurring now have governed the erosion process for the life of the valley.

Position Symmetry

ex.

An astronomer applies the laws that appear to govern motion on the Earth to the motion of stars in distant galaxies.

Occam's Razor

Simpler explanations are more likely to be true than complex ones.

Non-contradiction

ex.

Federal law requires that the hot water taps in nursing homes produce water hotter than 160° F to prevent bacterial growth. A separate law requires that hot water temperatures be below 110° F to prevent scalding.

Causality

cause and effect relationship

Rocks are held together by...

Electromagnetic interactions

Galaxies are held together by...

Gravity

Newton's First Law:

All objects remain in uniform motion, unless compelled to do otherwise by an outside force.

Newton's Second Law of Motion:

The acceleration of an object depends on the mass of the object and the amount of force applied.

F=MA

Newton's Second Law of Motion Formula

force = mass * acceleration

Newton's Second Law (connections)

This is the most powerful of Newton's three Laws, because it allows quantitative calculations of dynamics.

How do velocities change when forces are applied?

- Notice the fundamental difference between Newton's 2nd Law and the dynamics of Aristotle: according to Newton, a force causes only a change in velocity (an acceleration); it does not maintain the velocity as Aristotle held.

Newton's Third Law of Motion:

For every action, there is an equal and opposite reaction

When you travel at extremely high speeds, your length gets shorter and time slows down from an observers reference frame. And your mass increases. From the inertial reference frame you feel like the observer and witness their point of view about you.

Velocity

the speed and direction of a moving object

Acceleration

Acceleration = 9.8 M / S^2

it is the rate of change in velocity per unit of time

Centripetal Force

a force that acts on a body moving in a circular path and is directed toward the center around which the body is moving.

center seeking

ex. Spinning bucket of water.

ex. Doing a donut. Body turns into circle.

Centrifugal Force

an apparent force that acts outward on a body moving around a center, arising from the body's inertia.

center fleeing

Contact Force

interactions between objects that touch each other

- The electromagnetic repulsion between the electrons of one atom and the next

ex. applied, friction, spring, normal, drag forces. Just like they sound

Electrical Model of Matter (+/-)

- Contains 2 types of charged particles:

1. Positive charged nuclei

2. Negative charged electrons

Terminal Velocity

The greatest velocity a falling object can achieve

- The forces of friction and gravity cause you to stop accelerating while falling

Forces vs. Net Force

Net Force: the sum of all forces acting on an object.

- An object can have multiple forces acting on it but there is only one net force.

Net force and acceleration are ALWAYS in the same direction

Types of Net Force (3)

BUN

1. Balanced force

2. Unbalanced forces

3. No net force

Balanced force

no net force (uniform motion)

Unbalanced forces

net force (accelerated motion)

No net force

no acceleration

If a semi and a cooper collide

they exert the same forces on each other. But the cooper will accelerate backward more because it has greater mass (This is an example of Newton's 3rd law)

You are in a rotating cylinder wearing roller skates. What are the forces upon you?

1. Gravity

2. Contact force: you are pushing on the floor and the floor is pushing back on you.

What are the forces, velocities, and acceleration upon you as you ride an elevator?

(Before you move the forces are balanced)

1. Gravity

2. Contact force

(As the elevator accelerates you (contact force) have to overcome gravity)

3. As you move between forces you are in uniform motion again.

(As you stop Gravity must overcome contact force)

You are sitting in a chair. What is the reaction force to gravity pulling on you that is required by Newton's 3rd Law?

If the earth is pulling on you you must be pulling back on the Earth

What can you say about an object's weight and mass as it moves farther from the earth?

1. Mass stays the same/constant

2. Weight decreases: if you are further away from the earth the object's gravity has less pull on you.

What are the forces on a car passenger as it turns a corner at a constant speed?

1. Centripetal force: you are accelerating because this force makes you change direction.

2. Gravity

3. Contact Force

Circular motion

any motion in which an object is moving along a curved path

- Acceleration or a single force pulling inward

You have two charged balls that are one meter apart. How does the force on either ball change if you bring them closer together so that they are now 0.5m apart.

1. It gets stronger

2. You do not need to know the change on the balls for electrical force. It is ALWAYS strongest when they are closer together no matter if the force is repulsive or attractive.

3. Fe=KQq/d^2

You have two charged objects one meter apart. How does their potential energy change if you decrease the separation by half to 0.5m?

1. NOT enough information. Are the charges the same or different?

2. The electrical force depends on distance: lower the distance the greater the force.

3. Potential energy DEPENDS on the charges:

repulsive: potential energy will be greater when they are farther apart.

attractive: potential energy will be greater when they are closer together.

Objects moving at a high speed as observed from a "stationary" frame of reference are measured to be: (5 Predictions)

CSSSF

1. Conservation of mass and energy together

2. Short (length contraction)

3. Slow (time dilation)

4. Simultaneity

5. Fat (mass increase) ... e=mc2

Types of Conservation - things you can count on being the same before and after a process

1. Conservation of mass

2. Energy

3. Mass number

4. Charge

5. Linear Motion

6. Conservation of mass and energy are only conserved together at a night speed. Otherwise consider mass and energy to be conserved separate.

Momentum (2 Types)

1. Linear

2. Angular

Linear Momentum

ex. Game of pool

Energy Transformations

A jumping frog: How does it happen?

CEKGKT

1. Chemical potential energy (ingested food)

2. Elastic Potential energy (muscles)

3. Kinetic energy (the jump upwards)

4. Gravitational potential energy

5. Kinetic energy (coming down)

6. Thermal energy (dissipated through ground)

Angular Momentum

the momentum spinning things have. Also a conserved quantity, which means angular momentum will keep something spinning in the same plane unless there is another force working against it.

ex. Tucking in diving

Energy

an object's capacity to change things around it

Types of Energy (2 Types)

1. Potential

2. Kinetic

Potential Energy

stored energy. The energy an object has to do something

Potential Energy (5 Categories)

1. Gravitational Potential Energy

2. Electrical Potential Energy

3. Elastic Potential Energy

4. Chemical Potential Energy

5. Nuclear Potential Energy

Kinetic Energy

Energy in action. The energy of any moving object. If those moving objects are molecules we call it "heat" or "thermal energy."

Heat Transfer (3 Types)

1. Conduction

2. Convection

3. Radiation

Conduction

The direct transfer of heat from one substance to another substance that it is touching.

Convection

Process by which, in a fluid being heated, the warmer part of the mass will rise and the cooler portions will sink.

Radiation

The transfer of energy by electromagnetic waves

Archimedes Principle

any object fully or partially submersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object

Bouyant Force

weight of the displayed water

- Gravity pushes down, buoyant force pushes up = neutral buoyancy (not accelerating up or down)

Forces in Fluids

Fluids: anything that flows

1. Bounded: Lakes, tubs, tubes etc.

2. Pressure bounded: equalizes to all points.

3. Pressure unbounded: depends on depth ONLY

4. Buoyant Force: Weight of Displaced water (determined by the object's volume).

BF is always UP because the greater pressure comes from the lower depth. BF is affected ONLY by the VOLUME of the object. Depth and Weight do not mater.

Whether an object will float or sink depends on the net force.

Mass of two falling balls

1. Mass has nothing to do with when an object hits the ground, only depends on how close the object is to the earth.

2. Bigger mass = greater force of gravity

3. Balls will hit the ground at the same time

When does the gravity really go to zero?

NEVER

Change in distance will effect

a change in force.

A change in force will effect a change in distance

4 Types of Waves (4)

1. Compression Longitudinal

2. Transverse Shear

3. Surface Waves

4. Standing Waves

Compression Longitudinal

Waves in which the medium moves parallel or in the same direction as the wave.

waves that can go through all states of matter: solids, liquids, gas, and plasma.

Transverse Shear

A shear wave. The molecules in the medium vibrate at right angles to the direction the wave propagates.

- waves that can only go through solids

Surface Waves

Waves that travel along the surface of a medium

ex. looks like ripples on a pond

Standing Waves

When a wave combines back on itself by reflecting or wrapping around.

Wave Properties (4)

1. Amplitude FAWS

2. Wavelength

3. Frequency

4. Speed

Amplitude of a Wave

the maximum displacement of the medium from its rest position when a wave passes through it.

Wavelength

the distance between the crest of one wave and the crest of the next wave

Frequency of a Wave

Number of complete waves (crest) that pass a point per second

Speed of a Wave

The rate at which a specific wave disturbance travels from point to point

(frequency x wavelength)

Crest of a Wave

The top part of the wave

Trough of a Wave

The bottom part of the wave

The Wave Phenomena

1. Reflection

2. Refraction

3. Interference

- Constructive interference

- Destructive interference

Diffraction and interference are the two things that ONLY WAVES do

Reflection (of a wave)

When a wave bounces off a surface.

Refraction

When a wave changes direction when passing from one medium to another.

Wave Interference

When 2 waves meet in the same place at the same time

Constructive Wave Interference

Where 2 Crests (Peaks) or 2 Troughs line up

Destructive Wave Interference

if peak meets at trough or vice versa, they cancel each other out

Wave Diffraction

Propagation of a wave around an obstacle

The changing of direction of waves to bend around corners and spread as they encounter obstacles.

Propagation

the wave spreads outward in both directions

Doppler Effect

change in the apparent frequency of a wave as observer and source move toward or away from each other

- the frequency of a car horn sounds higher when it is coming towards you and lower when it passes you

Compression Forces

Crush

Tension Forces

Pull or Twist

Shear Forces

Tear or Cut

ex. Ex. Oobleck - cornstarch and water. Tears/cuts when handled gently, but hardens when using force. Makes sense if you watch it in slow motion. The water runs away and leaves the cornstarch to take the hit.

The Dual Nature of Light

light has properties of both particles and waves

The Photoelectric Experiment

(The Dual Nature of Light)

1. Shine a flashlight on electrons: nothing happens

2. Shine a brighter light on the electrons: nothing happens

3. Shine a UV light: electrons jump off

- proof that light acts like a particle

- the particles carry their energy in frequency: characteristic of particles

- the particles carry their energy in their amplitude: characteristic of waves

What did the photoelectric experiment prove?

That light has particle properties

The Electromagnetic Spectrum

the complete range of electromagnetic waves placed in order of increasing frequency

GXUVIMR

Gardens Expensive Under Very Important Male Rabbits

1. Gamma Rays

2. X-rays

3. Ultraviolet

4. Visible light

5. Inferred

6. Microwaves

7. Radiowaves

Order of the Models of Matter

CMPRBQ

Can Monkeys Prepare Radishes Better, Quantifiably?

1. Continuous

2. Molecular

3. Plum Pudding

4. Rutherford

5. Bohr Model

6. Quantum Model

Continuous Model of Matter

Newtonian physics:

- what you see is what you get

Molecular Model of Matter

Ex. Dance floor at The Wall

1. Solid state: always moving, but minimal motion. That's why solids hold their state.

- Once molecules get moving we can measure their kinetic energy (heat, thermal)

2. Liquid state: flow through room more than they did in solid state.

- Still relatively close together and fill only part of the space.

3. Gas state: the faster the molecules move the more space they need to make room for all their kinetic energy.

Plum Pudding (JJ Thomson) Model of Matter

Plum Pudding (Thomson Model)

- Molecules can be broken into parts of positive and negative charged fragments

-HE THOUGHT: One giant positively charged chunk (soup) and lots of little negatively charged pieces (within the soup)

Rutherford

Golf foil experiment, discovered nucleus

1. Sent alpha particles (positively charged) through a golf foil

2. Most were expected to pass right through

3. A few bounced straight back!

4. Previous model could not account for something incredibly dense and positive in the center

5. The positively charged particles were repelled by something positive in the foil

- Solar System Model Dense, positive nucleus

- Electrons orbiting around the outside

- Most of atom is empty space (doesn't explain discrete spectra: electrons aren't giving off light, if they are just flying around they would give off light)

The Bohr Model

model of an atom that shows electrons in circular orbits around the nucleus

The "fix" to the solar system model: electrons are in specific, non-radiating orbits

1. Energy of a photon is a function of its frequency

2. Explains discrete spectra

- A photon jumps up and absorbs energy (lots of colors and bars of black)

- Then it falls back down and gives off light (lots of black and bars of color)

- Color of light is measured by the frequency it had to lose to get back down

- If it goes from REALLY high to REALLY low it had to give off energy/high frequency light

Quantum Model

current atomic model in which a tiny, dense atomic nucleus is surrounded by a "cloud" of electrons occupying three-dimensional orbitals according to their energies

Since light is a wave and a particle; maybe matter is too!

Double slit experiment:

1. Electrons are in orbit

2. Orbitals are standing waves of probability

3. Are arranged according to the exclusion principle

4. Let's draw an energy well! (Some People Dance Funny)

a. S (You can fit 1 orbitals)

b. P (You can fit 3 orbitals)

c. D (You can fit 5 orbitals)

d. F (You can fit 7 orbitals)

e. Each orbital can only hold 2 electrons

5. Atomic volume: diameter of nucleus and all electrons around it. As we add shells diameter (atomic volume) gets bigger. As you go from left to right, add electrons, so shells suck closer to the nucleus and atomic volume gets smaller.

Three things that mean disorder is increasing (order will NEVER increase)

1. 2nd Law of Thermodynamics

2. Entropy

3. Law of Increasing Disorder

Entropy

A measure of disorder

ex. All natural processing happen in one direction. That's why watching videos backwards looks weird.

Mass Spectrometry

Can't separate one molecule from the others, so take TONS of molecules, put them through molecule breaking machine and measure mass of all different parts of molecule.

Intensity: y axis

Mass: x axis

Look for the parent peek, which is LARGEST mass (represents entire molecule)

Find atomic mass of each atom (number on bottom of little box on periodic table)

Balancing Equations

Products on left, reactants on right

Diatomic molecules:

IBCFONH

I Bring Clay For Our New House

i. SEVEN SHAPE!!!

ii. I

iii. Br (Bring)

iv. Cl (Clay)

v. F (For)

vi. O (Our)

vii. N (New)

viii. H (House)

ix. You will NEVER see these atoms alone, they must be with another one!!

x. You may see a question that says which equation is balanced and correct...you MUST make sure the diatomic molecules are not alone!

Activation Energy

energy it takes to bring reactant to transition state

This is the chart with funny curve, represent chemical reactions.

- if it takes a long time then activation energy bump will be little

Energy released will be represented in the form of light or heat.

Transition State

where a reaction begins

Exothermic

releases energy, end lines up below middle line