Work and Energy Flashcards
Kinetic energy=? Units=?
K=1/2mv^2
units=J=Newton x meter
Gravitational PE=? Units=?
U=mgh
units=J=Newton x meter
Elastic PE=? units=?
U=1/2kx^2 (k=spring constant, x=amt of compression or stretch)
units=J=Newton x meter
Total mechanical energy=? units=?
E=U+K
units=J=Newton x meter
Conservation of mechanical energy=?
change in E=change in U+ change in K=0
Work(nonconservative)=? units=?
W=change in E=change in U+ change in K=0
units=J=Newton x meter
Mechanical work=? units=?
W=Fdcos(theta)
units=J=Newton x meter
Piston work=? units=?
W=P x deltaV
units=J=Newton x meter
Power=? units=?
P= Work/time = change in energy/time
Units=Watt=J/s
Net work=? units=?
W(net)=change in kinetic energy=Kf-Ki
units=J=Newton x meter
Mechanical advantage=? units=?
F (out)/ F (in)
unit-less! (it is a ratio)
Efficiency=?
W (out)/ W(in) = (load x load distance)/(effort x effort distance)`
What does the spring constant depend on?
the stiffness of the spring
When does a spring have elastic potential energy?
When it is stretched or compressed from its equilibrium length (the length at which it is completely relaxed.)
What is work? units?
the amount of energy transferred from one system to another.
units=J=Newton x meter
What is power?
Rate at which energy is transferred from one system to another.
What are conservative forces?
Path independent, do not dissipate mechanical energy of a system.
Conserve mechanical energy.
EX: gravity, electrostatic forces, elastic (nearly)
What are non-conservative forces?
Path dependent.
Cause dissipation of mechanical energy (as heat or chemical energy.)
EX: friction, air resistance, viscous drag.
What is mechanical advantage?
What is increased by a simple system? what is decreased?
The factor by which simple systems increase the ability to do work.
Force required - decreased.
Distance through which force is applied - increased.
Machines: plane, wedge, wheel and axle, lever, pulley, screw.
What is efficiency?
ratio of a simple machine’s work output to work input when nonconservative forces are taken into account.
What is electrical potential energy?
The amount of energy needed to bring a charge from infinitely far away to a given position close to a source charge.
Electrostatic force
F= kq1q2/r^2
Electrostatic potential energy
U=Fxr
U= kq1q2/r
Electrostatic potential
V=U/q
V= kq1/r
Electric field
V=Ed (capacitor)
E=kq1/r2
