Everyday physics final study guide
a study guide for the university of iowa "physics of everyday life" class
Terms
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- Projectile
- an object that is thrown or struck or shot and then travels under the influence of gravity
- Net force
- the total force (positive and negative) acting upon an object
- Physics
- The study of how objects behave (from the very tiny to the very big, and from the beginning of the Universe to its ultimate fate).
- Mechanics
- why things move
- Aristotle
- believed that the natural state of objects was to be at rest
- Galileo
- the first to do experimental studies of the laws of motion and was Imprisoned by Pope Urban VIII in 1633 for advocating the Copernican theory, also know as the heliocentric theory, that the earth was a planet revolving around the sun.
- Brahe
- Compiled the first detailed observational data on planetary motion (mars), without a telescope.
- Kepler
- analized brahe's data and verified the heliocentric theory. These regularities are known as Helpers Laws of Planetary motion.
- Newton
- wrote Principia in 1687. Made the 3 laws of mechanics and law of gravity. He also invented calculus.
- Einstein
- shows in 1905 that newtons laws were not valid for objects moving with speeds near the speed of light.
- Speed of light
- 18600 miles/sec
- Quantum mechanics
- new theory that explained behavior at the atomic level
- Why does something move?
- because nothing stops it
- Torque
- the combination of force and point of application
- Net force=0 net torque≠0
- rod with forces applied at opposite ends in opposite directions
- Net force≠0 net torque=0
- rod with forces applied at opposite ends in the same direction
- Equilibrium
- net force=0 net torque=0
- Center of gravity (CG)
- the center of an object
- Stable
- not easy to knock over
- Condition for stability
- if the CG is above the edge, the object will not fall
- Stable structures
- are wider at the base (which lowers their center of gravity)
- Rotational inertia (moment of inertia)
- how much torque it takes to get an object rotating
- Acceleration due to gravity on the earth
- -10 m/s^2
- Weight
- mass x gravity
- Newton's Second Law
- f=mass x acceleration
- Velocity=
- distance traveled / time
- Acceleration
- change in velocity / time
- Present velocity
- initial velocity = acceleration x time
- Distance traveled
- ½ acceleration x time^2
- Time for an object thrown to reach maximum height
- time= the square root of 2 x height / acceleration due to gravity
- Velocity required for an object to reach height h
- initial velocity= the square root of 2gh
- Centripedal acceleration=
- velocity squared / radius
- Torque
- force x lever arm
- Momentum
- mass x velocity
- Total momentum before collision
- equals total momentum after collision
- Pressure=
- force per unit area
- Fluid force
- pressure x area
- Buoyant force
- weight of displaced water=volume of displaced water in liters x 10 n / liter
- Convert Fahrenheit to Celsius
- 5/9 [T(F)-32]
- Convert Celsius to Fahrenheit
- 9/5T(C)+32
- Convert Celsius to Kelven
- T(C) +273
- Heat
- mass x specific heat x temperature change
- Engine efficiency
- work done / heat in
- Change in internal energy
- heat into system - work done by system
- Power (watts)
- current x voltage energy/time (joules per second)
- Voltage
- current x resistance
- Resistance
- voltage / current
- Wave speed=
- wavelength x frequency
- Frequency
- 1 / period (time)
- Period
- time required to complete one cycle
- Photon energy
- hf
- Wavelength
- c / f
- frequency of light
- speed of light / wavelength
- c=3x10^8 m/s
- ?
- velocity through a medium
- c/n
- period of a pendulum T of length L
- 2π x square root L/g
- azX
- z+n
- period p of a mass m oscillating on a horizontal spring of force constant k
- t=2π square root m/k frequency= square root k/m;/2π
- order of states of matter stronger to lesser forces between atoms
- solids, liquids, gases
- measure of density
- kg/m^3
- density of lead
- 11,000 kg/m^3
- density of water
- 1,000 kg/m^3
- density of air
- 1.25 kg/m^3
- density of aluminum
- 2,700 kg/m^3
- measurement of pressure
- Pascal (Pa) or pounds per square inch (psi)
- pressure depends on
- number density x temperature
- atmospheric pressure (atm)
- 100,000 n/m^2
- static fluid formula
- Fbottom=Ftop+mg where mg is the weight of the volume
- variation of pressure with depth
- Fbottom-Ftop=mg=(density x vol) x g
- pressure does what when depth is increased
- it increases
- pressure at depth h
- p + density x g h
- when ice in water melts what happens?
- the level stays the same
- volume fluid flow rate
- gallons per minute (gpm), liters/s, cubic feet per minute (cfm) or m^3/s
- volume fluid flow rate formula
- tube cross section area A, flow speed u vfr= u x A (m/s x m^2)
- mass flow rate formula
- p x u x A
- incoming and outgoing flow rate formula
- v1 x A1=v2 x A2
- the pressure of liquids _____ when it goes faster
- decreases
- continuity
- v x A= constant
- definition of Bernoulii's equation
- as the speed of a moving fluid increases, the pressure within the fluid decreases
- bernoulli's equation
- fluid flow velocity=u, fluid density=p (rho), fluid pressure=P P + ½ p x u^2 + p x g x h= constant
- viscosity
- a tendency for liquids to resist flowing.
- Flow through a pipe
- π(P2-P1)D^4/128Ln n=fluid's viscosity
- The US uses how much of the total world energy consumption?
- 25%
- Internal energy
- the sum of the energy of all the molecules in the system
- Energy of motion (kinetic energy)
- ½ m v^2
- Thermodynamics
- the study of heat and its transformation into mechanical energy
- Conservation of energy
- you can't get more work out than the energy you put in
- Engine efficiency cannot be 100%
- you cant get as much out as you put in
- Heat
- the energy that flows from one system to another because of their temperature difference.
- First Law of thermodynamics
- If energy is transferred and the internal energy of system B decreases by some amount then the internal energy of system A must incrase by the same amount.
- Second law of thermodynamics
- if the temperature of system A is less then the temperature of system B then heat flows from B to A (hot to cold)
- Convection
- heat is carried from place to place by the bulk movement of either liquids or gasses
- Conduction
- heat is transferred directly through a material with no bulk movement of material
- Thermal conductivity
- the effectiveness of a material in conducting heat
- Radiation
- the heat transfer by electromagnetic waves - thermal light waves
- Thermal radiation
- T^4
- Emissive
- the efficiency with which an object emits thermal radiation. Is a number between 0 and 1. A good emitter has an e close to 1.
- Heat capacity (specific heat)
- the amount of heat that is required to raise the temperature of one g of a substance by 1 degree C.
- Heat capacity equation
- heat Q= mass of sample x specific heat x temp change
- 1 BTU
- the heat needed to raise the temperature of 1 pound of water by 1 degree F
- law of conservation of energy
- the change in internal energy= the heat absorbed- the work done
- entropy
- the total disorder of an object
- restoring force
- the force that brings a system back to equilibrium
- amplitude
- maximum displacement from equilibrium
- mechanical wave
- a disturbance that propagates through a medium
- wave
- a disturbance that moves through something
- infrasound
- sounds below 30 Hz
- ultrasound
- sounds above 20,000 Hz
- wavelength
- length of a wave