2 Work & Energy Flashcards
kinetic energy equation
(1/2)mv^2
joules
gravitational potential energy equation
U = mgh
h: height above zero potential energy (datum)
elastic potential energy equation
U = (1/2)kx^2
“relaxed” spring = equilibrium
total mechanical energy
E = K + U
1st Law of Thermodynamics
conservation of mechanical energy
deltaE = deltaK + deltaU = 0
W(nonconservative) =
e.g. air resistance, friction, etc.
deltaE = deltaK + deltaU
exactly equals the energy lost from the system
path-dependent forces (longer distance traveled is greater energy lost)
work equation
W = Fd cos(theta)
*theta: angle between applied force vector and displacement vector
isochoric
volume stays constant
isobaric
pressure stays constant
power
rate at which energy is transferred from one system to another
power equation
P = W / t = deltaE / t
work-energy theorem
deltaW(net) = deltaK = K(f) - K(i)
mechanical advantage
ratio of magnitudes of force exerted on an object by a simple machine (F(out)) to the force actually applied on the simple machine (F(in))
F(out) / F(in)
decreased F(in) needs increased distance upon which force is applied to achieve same F(out)
pulleys
T(1) + T(2) = mg
two-pulley system
increasing number of pulleys decreases tension in each rope
–> increases mechanical advantage
