Concepts of Science Exam 1 Study Guide

Johannes Kepler

\-Took over after Tycho Brahe’s death

\-Established three laws based on the data he collected

Kepler’s First Law

Planets move in elliptical orbits with sun at 1 focus

Kepler’s Second Law

Line connecting planet/sun sweeps out equal areas in equal times

\-planets move slower when further away from the sun and faster when closer to sun

Kepler’s Third Law

Square of period (time planet takes to go around sun) is proportional to cube of the semimajor axis (distance from center through focus

Galileo Galilei

\-First to record observations with a telescope

\-Supported a sun-centered universe

Speed

The distance an objects travels divided by the time it takes to travel that distance

Velocity

The same value as speed, but includes information about direction (60 m/s northeast) because it is a vectoral quantity

Velocity Equation

distance/time

Speed Equation

distance/time

Acceleration Equation

(final velocity-initial velocity)/time

Velocity of an Accelerating Object

constant a \* time

Acceleration Constant (at 90 degrees)

9\.8 m/s^2

\*This only applies to objects on Earth’s surface

Distance Traveled Equation

1/2 \* acceleration \* t^2

Time Equation

distance/velocity

Newton’s First Law

Moving objects will continue moving in straight lines at constant speed, & stationary objects will remain at rest, unless acted on by an unbalanced force

Newton’s Second Law

\-The acceleration produced on a body by a force is proportional to the magnitude of the force and inversely proportional to the mass of the object

\-The greater the force, the greater the acceleration

\-The more massive an object, the smaller the acceleration

Force Equation

mass \* acceleration

Newton’s Third Law

\-For every action there is an equal and opposite reaction

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\-Interacting objects exert equal but opposite forces upon each other

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\-The results of the interactions of the objects may be different

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\-The equal and opposite forces do not cancel because they are acting on different objects

Momentum Equation

mass \* velocity

Conserved

A physical quantity doesn’t change

Newton’s Universal Law of Gravitation

Between any two objects in the universe there is an attractive force (gravity) that is proportional to the square of the distance between them

Force of Gravity (N) Equation

(Gravitational Constant \* mass 1 \* mass 2)/distance^2

Universal Gravitational Constant (G)

6\.67 \* 10^-11 N \* (m^2/kg^2)

g

\-Gravitational acceleration on Earth’s surface

\-9.8 N/kg

Equation for Work (joules)

force \* distance

Energy

The ability to do work

Power

The rate at which work is done

Power (watts) Equation

work/time or energy/time

Energy Equation

power \* time

Kinetic Energy Equation

1/2 \* mass \* speed^2

Potential Energy

Energy waiting to be released

Potential Energy Equation

mass \* g \* height

Heat is transferred from…

hot to cold

Hot objects have…

high kinetic energy

Types of Wave Energy

Water waves, sound waves, seismic waves, electromagnetic radiation (light)

Sound waves are created when…

atoms/molecules in the air are set in motion.

Seismic waves carry…

potentially destructive energy of moving atoms/molecules in the Earth that can be unleashed in earthquakes.

Electromagnetic radiation has energy stored in the form of…

alternating electric and magnetic fields.

Is mass a form of energy?

Yes

Equation for potential energy of objects at rest

Energy = mass \* (the speed of light)^2

or

E = m\*c^2

First Law of Thermodynamics

In an isolated system, the total amount of energy is conserved.

Open Systems in Thermodynamics

There is exchange of matter and energy with surroundings.

Closed or Isolated Systems in Thermodynamics

There is no exchange of matter and energy with surroundings

Fahrenheit

Daniel Fahrenheit used the coldest mixture of ice and salt water he could produce as 0 degrees

Celsius

0 degrees is the freezing point of water

100 degrees is the boiling point of water

Kelvin

Uses the same temperature distribution as Celsius, but 0 Kelvin is -273 degrees C

Fahrenheit to Celsius

(1.8 \* degrees C) + 32

Celsius to Fahrenheit

(degrees F/1.8) - 32

Conduction

\-Movement of heat by atomic scale collisions

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\-Heat flows at different rates in objects depending on their thermal conductivity

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\-Metal is a great heat conductor and wood is a great heat insulator

Conduction Example

• If a piece of metal is heated on one end, atoms there begin to move faster

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• By colliding with neighboring atoms, some of the kinetic energy is transferred & atoms further away progressively begin to move faster

Convection

Transfer of heat by bulk motion of a gas/fluid

Convection Example

\- Boiling water

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– Water near bottom of pot expands becomes less dense

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– Cooler, more dense water above sinks

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– Hot water rises in bulk, carrying faster moving molecules



– Heat then transferred to air & cycle repeats

Are things that are bad heat conductors good insulators?

Yes

Radiation

\-Transfer of heat by electromagnetic waves

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\-It can be transmitted through empty space

Second Law of Thermodynamics

\- The behavior of energy is regular and predictable

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\-Heat energy can flow by conduction, convection, and radiation

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– Heat will not flow spontaneously from a cold to a hot body

* Doesn’t mean it is impossible for heat to flow from cold to hot object, just that it won’t occur spontaneously & requires the input of additional energy

– You cannot construct an engine that does nothing but convert heat to useful work

* Some energy is lost to surroundings

– Every isolated system becomes more disordered with time

Efficiency

Term to quantify amount of energy loss in an engine

Efficiency Equation

((𝑇ℎ𝑜𝑡 ―𝑇𝑐𝑜𝑙𝑑)/𝑇ℎ𝑜𝑡) × 100

Ordered vs. Disordered System

• In an ordered system, objects are arranged in a regular predictable pattern

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• In a disordered system, objects are arranged randomly

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• Because there are more ways to arrange things randomly, disorder is more probable & easily

Entropy

\- Term given to quantify the amount of a system’s disorder

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\- 2nd Law can be restated that the entropy of an isolated system remains constant or increases

Static Electricity

\-Force between charged objects (charges) was named electricity from Greek word for amber (electro)

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\-This force can be attractive or repulsive, which is very different from gravity (which is always attractive)

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\-Electrons can be transferred to other objects giving them a negative charge while the original thing now has a positive charge so they now stick together

Coulomb’s Law

Force between 2 electrically charged objects is proportional to the product of their charges divided by the square of the distance between them

Coulomb’s Law Equation

Force = (Charge 1 \* Charge 2)/distance^2

How many poles does every magnet have?

2; north and south

What happens when a magnet is placed on a magnetic field?

It will rotate and align its poles along the field. The density of the lines indicate the strength of the field.

Electric Circuit

An unbroken path of material that carries electricity that is made of electrical conductors

What are the three components of an electric circuit?

– A source of energy (e.g., a battery)

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– A closed path through which current flows

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– A device that uses the electrical energy

Current

\- Amount of charge that flows per unit time

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\- Measured in amps

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\- 1 amp of current = 1 coulomb of charge per second

Voltage

Amount of “electrical pressure” in circuit

Electrical Resistance

\-Describes the ease with which current flows in a wire

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\-Measured in Ohms

Ohm’s Law

The greater the resistance in a wire, the more electrical kinetic energy is lost as heat

Ohm’s Law Equation

voltage = current \* resistance

Power Equation

Power = current \* voltage

Series Circuit

two or more loads are linked along a single loop of wire

Parallel Circuit

different loads are situated on different wire loops

Maxwell’s Equations State

– There are no magnetic monopoles in nature

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– Coulomb’s law: like charges repel, unlike attract

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– Electrical phenomena can be produced by magnetic effects

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– Magnetic phenomena can be produced by electrical effects

Wavelength

The distance between crests (highest points) of adjacent waves

Frequency

The number of wave crests that go by a given point per unit time (cycles per second or hertz, Hz)

Period

The time between adjacent waves (inverse of frequency, measured in seconds per wave)

Velocity (waves)

The speed & direction of the wave

Velocity of a Wave Equation

wave velocity = wavelength \* frequency

Amplitude

The height of the wave crest above the undisturbed position (midpoint between crest and trough)

Transverse Wave

motion of the medium is perpendicular to the wave direction

Longitudinal Wave

motion of the medium is parallel to the wave direction

Electromagnetic Waves

\-consist of alternating electric and magnetic fields that are perpendicular to each other and the direction the wave is moving

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\-can move through empty space without a medium

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\-light is an example which slows down when passing through matter

Interference

\-The process by which waves from different sources overlap and affect each other

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\-The observed height at point where two waves come together is the sum of the individual amplitudes

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\-Waves can enhance one another/add constructively (constructive interference) or cancel each other out (destructive interference)

The Doppler Effect

\-When a source emits a wave, stationary observers will detect the same pitch

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\-If source is moving, the detected pitch will increase/ decrease as the source moves towards/away from the observer

Electromagnetic Spectrum

Maxwell’s equations predicted electromagnetic waves beyond what was seen should be possible

Radio

\- Have longest wavelengths (from bigger than Earth to few meters long)

\- Frequencies from kilohertz to hundreds of megahertz

\- Broadcasters transmit information in narrow frequency ranges (radio stations)

\- Radio waves carry signals encoded by amplitude or frequency modulation

Microwave

• Have wavelength range from 1 meter to 1 millimeter

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• Travel readily in air but absorbed/reflected by rocks/metal objects

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• Used in aircraft radar & cell phones

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• Many satellites broadcast signals in microwave range

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• Can be used to stimulate the rotation of molecules (e.g., H2O)

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• Microwave ovens accelerate electrons to generate microwaves and heat water in food

Infrared

• Have wavelength range from milimeters to microns

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• Corresponds to the vibrational energy levels of molecules

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• Warm objects emit infrared radiation

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• Infrared detectors can be used for missile guidance systems and for night vision

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• Can be used to find heat leaks in buildings

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• Eyes of many insects & nocturnal animals sensitive to infrared light and use it to see in the dark

Visible

• Contains the colors of the rainbow from 700 nanometers (red) to 400 nanometers (violet) light

• Sunlight is especially intense in this region

• Eyes of diurnal animals sensitive to this thin slice of the electromagnetic spectrum

Ultraviolet

• Have wavelength range from 400 to 100 nanometers

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• Longer UV light can cause changes in skin pigments leading to tanning, while shorter wavelengths can cause cellular radiation damage (sunburn, cancer)

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• Often used as a sterilization technique to kill bacteria

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• The sun produces UV light, though the atmosphere absorbs of this light

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• If in sun too long, should protect skin with sun-block that absorbs/reflects UV light

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• Fluorescent materials can absorb UV light & emit visible light

X-Ray

• Have wavelength range from 100 to 0.1 nanometers, smaller than a single atom

• Penetrate into most matter, but absorbed differently

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• Allow for medical imaging techniques to visualize bones/organs

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• Generated with a “lightbulb” where a tungsten filament is heated to emit electrons that are moved through the tube using a high voltage & smash into a metal plate; the rapid deceleration produces X-rays

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• Intense X-rays made at synchrotrons, where electrons are accelerated in a circle

Gamma

• Most energetic electromagnetic radiation

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• Wavelengths range from size of atom (0.1 nm) to size of nucleus (a trillionth of a meter)

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• Emitted on Earth in high-energy nuclear/particle reactions, but produced abundantly in stars

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• Used in nuclear medicine by giving patients radioactive chemicals that accumulate in certain parts of body emit gamma rays

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• Can be used to treat cancer (kill cancer cells)

Transmission

Light passing unaltered through matter (e.g., through a window or the Earth’s atmosphere)

Refraction

Light bending as it passes from one medium to another (e.g., moving from air through water, lenses, or a prism); the “bend angle” depends on the wavelength

Absorption

Light being soaked up by matter, which is typically converted to heat (e.g., asphalt during summer); black/dark colors absorb more visible light

Scattering

Light absorbed & reemitted in other directions (e.g., diffuse scattering by clouds); white objects scatter all visible wavelengths, colored objects scatter some and absorb others

Reflection

Light bouncing off a surface, which creates a “mirror image” of the emitting objects

In the periodic table, elements are organized in columns/rows by…

their weights/properties