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23 Cards in this Set
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Equilibrium

no translational or angular acceleration.
a system is in equilibrium if the translational velocity of its center of mass and angular velocities of all its parts are constant the net force acting on a system in equilibrium is ZERO. Fupward = Fdownward Frightward = Fleftward 

Static equilibrium

If all velocities in a system are zero.


Dynamic equilibrium

If any velocities are nonzero, but all velocities are constant.


Systems not in equilibrium

this means that the center of mass is accelerating translationally or its parts are accelerating rotationally.
Steps for facing a problem that is not in equilibrium: 1. write the equations as if the systems are in equilibrium 2. before solving, add 'ma' to the side with less force. 

Torque

a twisting force, a vector but the MCAT allows us to think of torque as clockwise or counterclockwise.
When the lever arm is used, equation for torque is: T =Fl F = the force applied l = is where the position vector is form the point of rotation to the point where the force acts at 90 degrees. (lever arm) 

Lever arm

a position vector that is from the point of rotation to the point where the force acts at 90 degrees.


Units of energy

Joule
electron volt 

Mechanical energy

the kinetic energy and potential energy of macroscopic systems.


Kinetic energy (K)

the energy of motion
K = 1/2mv^2 

Potential energy (U)

the energy of position
all potential energies are position dependent. 

Gravitational potential energy (Ug)

the energy due to force of gravity
Ug =mgh 

Elastic potential energy Ue

the energy due to the resistive force applied by a deformed object.
Ue = 1/2kdelta(x)^2 k = hooke's law constant for the object x = displacement from the object's relaxed position 

Law of Conservation of Energy

since the universe is an isolated system, the energy of the universe remains constant


Work

the transfer of energy via force
W = Fdcos(theta) where F = force d = displacement of the system theta = angle between F and d 

Heat

the transfer of energy by natural flow from a warmer body to a colder body


Frictional forces

an exception to the work equation because frictional forces change internal energy as well as mechanical energy.


Equation describing total energy transfer due to forces and none to heat

W = deltaK + deltaU + deltaEi


Equation describing total energy transfer due to forces and none to heat or friction

W = deltaK + deltaU


Conservative Force

mechanical energy is conserved within the system
When a force acts on a system and the system moves from point A to point B and back, the total work done by the force is zero and it is conservative. the energy change is the same regardless of the path taken. 

Law of Conservation of Mechanical Energy

States that when only conservative forces are acting, the sum of mechanical energies remains constant.
K1 + U1 = K2 + U2 or 0 = DeltaK + deltaU 

Nonconservative forces

forces that change mechanical energy of a system when they do work
examples: friction pushing and pulling of animals W = delta(K) + delta(U) 

Kinetic frictional forces

increase the internal energy of the systems to which they are applied
does negative work on a sliding box FkD = delta(K) + delta(U) 

Power

Rate of energy transfer
unit of power is the Watt (W) which is equivalent to J/s. P = delta(E)/t equation for instantaneous power due to a force: P=Fvcos(theta) 