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Why are damns thicker at the bottom?
In order to withstand the greater force exerted by the water against the lower portion of the structure
The pressure exerted by water increases with depth
Buoyancy
The upward force exerted by fluid on an object
Force= weight of the fluid displaced by the object and acts in opposite direction to gravity
How much weight does a floating boat displace?
Displaces the amount of water equal to its weight
Does the density of liquid matter (salt vs. fresh water)?
YESS!
Salt water is denser than freshwater
Submerged objects displaced their volume
It is displaces a volume of fluid equal to its volume
How is buoyancy affected if an object is only partly submerged?
Buoyant force acting on it is equal to the weight of the fluid displaced by the submerged portion of an object
Temperature scales
0 K and -273.15 C represent the absolute zero
-273.15 C = 0 K
Temperature - measure of average molecular translational kinetic energy
Measure of the average kinetic energy of molecules in substance. Quantifies how fast particles move within a material
Temp. increases, the average kinetic energy of particles increase leading to rapid molecular motion
High specific heat
slow release of energy
Specific heat
the amount of heat required to raise the temp
Example of high specific heat
Large bodies of water with high specific heat can absorb and store heat during the day and release it at night, moderating costal temperatures
Why does heat cause expansion
Molecules absorb energy and vibrate more rapidly
Causes molecules to push against each other and move further apart, leading to expansion of substances
Why is ice less dense then liquid water?
Because of crystalline structure
Why are metals good conductors of heat and electricity?
Due to the presence of free electrons these electrons can move easily, carrying energy with them
Atoms not strongly bound
Conduction
Transfer of heat through direct contact transferred from higher temperature regions to lower
Convection
Transfer of heat through the movement of fluid
Radiation
Transfer of heat through electromagnetic waves
What is a fluid
Both liquids and gases
Relationship between reflection and absorption in a material
Good reflectors tend to be poor absorbers
The reflection and absorption of light or electromagnetic radiation by a material are inversely related
What do the 1st law of thermodynamics and the law of conservation energy have in common?
Energy cannot be created nor destroyed
All mechanical work causes heat
When mechanical work is performed on an object or by an object some of the energy is converted into heat due to inefficiency in the process
What is the maximum efficiency of a machine?
100%
What is wasted?
Heat
What is entropy?
Measure of the disorder or randomness of a system
Amount of energy in a system that is not available to do work
What is a wave?
Disturbance that travels through medium or space
What is a waves source?
Vibrating objects
Electromagnetic wave
Oscillating electric and magnetic field travel in a vacuum
Ex: Light, radio, microwaves
Mechanical wave
Sound and water require medium vibration of particles
What do waves transport
Energy
Wavelength
Distance between 2 consecutive points
Frequency
Number of oscillations or cycles it completes per unit of time (Hz)
Speed
Rate at which traveled through medium (wavelength and frequency)
Constructive
Crest of 2 waves align resulting in wave with greater amplitude
Destructive
Crest of one wave aligns with the through of another wave
Wave with reduced amplitude=complete cancellation
Wave interference
Two or more waves inter lapping in space
What makes electrons move?
A potential difference (voltage)
Potential difference created electric field within a conductor
Voltage
Does not flow like current does
Measurement of potential energy difference
Two points in a circuit
Resistance
Does not flow either
How much it resists the flow of current
Current
Flow of electric charge (usually electrons)
In response to a voltage
Where do electrons that power machines come from?
Electrons come from the flow of charge within a circuit
Sourced from atoms in conductive materials
Movement of ions
How fast do electrons flow in a circuit?
More relatively slowly
How does the thickness of a wire or pipe affect resistance?
Thicker wires or pipes have lower resistance
The electromagnetic spectrum
All forms of electromagnetic radiation
Radio waves
Microwaves
Infrared radiation
Visible light
UV radiation
Xrays
Gamma rays
Visible light
Small portions of electromagnetic spectrum that is visible to the human eye
Sensation of sight composed of different colors each corresponding to a specific wavelength
How does light get through glass? Does the frequency change?
Glass is transparent to visible light
Transmitted through it, absorbed by it, or reflected by its surface
Frequency of light does not change, decreases slightly due to interactions with the material
Incandescent bulbs
Work by passing an electric current through a thin filament which heats up and produces light due to its high temperature
Inefficient because they convert a significant portion of electrical energy into heat rather than light
Shorter life span
Fluorescent bulbs
Contain gas and a small amount of mercury vapor
More energy efficient than incandescent bulbs and produce less heat for the same amount of same amount of light output
Contains hazardous materials
LED bulbs
Passing an electric current through a semiconductor material
Highly energy efficient, converting a higher percentage of electrical energy into light and producing heat
Longer lifespan and more durable
How does energy flow?
Energy always flows from high to low
Coherence laser
Electromagnetic waves have the same frequency and phase
Interferes constructively and produces a highly focused beam
Monochromaticity laser
Monochromatic and consists of a single wavelength or color
Directonality laser
Highly directional
Travels in a narrow beam with minimal divergence
Concentrated energy over long distances
Ex: laser cutting, laser surgery, & laser ranging
Energy output in a laser
Intensity of the laser beam
Energy input in a laser
Electricity or pump energy supplied to the laser