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22 Cards in this Set
- Front
- Back
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Total Work
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W = w1 + w2 + w3 ...
W = ΔKE |
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Work
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W = Fdcosϴ
- ϴ is between W and d - if F ⟘ d, no work is done |
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Kinetic Energy
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ΔKE = ½mΔv²
- Energy describing a force's ability to do work - Energy of motion |
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Joule
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N*m
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Gravitational Potential Energy
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ΔPE = mgΔy
- Energy of POSITION. Not dependent on path taken (conservative force) |
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Total Mechanical Energy
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KEi + PEi = KEf + PEf
- In other words, the energy in equals the energy out - Stems from the first law of thermodynamics: energy cannot be created nor destroyed, it's just converted (like KE to PE!) |
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Simple Machines
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- Apply less force to get a job done, but over a greater distance
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Mechanical Advantage
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MA = effort distance/resistance difference
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Efficiency
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Efficency % = Work Output/Energy Input
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Thermal Energy
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- Energy of movement of molecules caused by vibrations
- Increase vibrations, increase KE, increase temp (since temp ∝ KE) |
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Heat (3)
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- Thermal energy that is transferred from one object to another
- Transmitted 3 ways: conduction, convection, radiation |
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Conduction
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Direct transfer of heat from one object to another
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Convection
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Heat transferred by motion of a fluid
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Radiation
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Heat transferred by light waves absorbing energy and transferring through electromagnetic waves
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Momentum
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p = mv
- Only moving objects have momentum - Think of it as a mixture of inertia and kinetic energy. |
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Impulse
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J = Δp = mΔv = FΔt
- Change in momentum over time - Since velocity is changing, this implies it's accelerating, and a force is there to do this. |
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Conservation of Momentum
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Δp = 0 or pi = pf
- In other words, the total momentum of all objects before a collision equals the total momentum afterwards - Momentum is ALWAYS conserved. |
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Collision
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- When two or more objects strike each other (directions matter)
- Three types: elastic, inelastic, and perfectly inelastic |
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Elastic Collision
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- Δp
- ΔKE conserved |
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Inelastic Collision
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- Δp conserved
- ΔKE not conserved |
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Perfectly Inelastic Collision
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- ΔP conserved
- ΔKE not conserved - Objects stick together after crashing, meaning that there is ONE velocity and m is (m1+m2) |
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Why is KE usually never conserved?
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- We're always losing energy to heat and sound!
- Matter can't be destroyed (so mass is the same) - And the energy of velocity is being transferred somewhere (so Δp is conserved) |
