work
measure of energy transfer that occurs when an object is moved over a distance by a force in the direction of the displacement
units for work
Joules (J)
energy
the capacity to do work or generate heat
units for energy
Joules (J)
types of mechanical energy
kinetic, gravitational potential, elastic potential
kinetic energy
energy due to motion
gravitational potential energy
potential energy related to an object's height
elastic potential energy
the energy of stretched or compressed objects
kinetic energy (formula)
KE=�mv�
gravitational potential energy (formula)
PE=mgh
elastic potential energy (formula)
PE=�kx�
Hooke's Law
F=-kx
Units on the spring constant
N/m
Units for displacement
meters (m)
Power
rate of energy transferred per unit of time
Power (formula)
P=?E/t (or W/t)
units for power
Watts (W)
formula for work
W=F?x(cos?)
momentum
the product of mass and velocity for an object
momentum (formula)
p=mv
work energy theorem
work is equal to change in energy
work energy theorem (formula)
W=?KE, W=?PEg, W=?PEs
base units for Watts
kg m�/s�
base units for Joules
kg m�/s�
units for momentum
kg m/s
1st law of thermodynamics
conservation of energy
2nd law of thermodynamics
no energy transformation is 100% efficient (some energy is always lost to the highly disordered/random form of energy: heat)
Conservation of momentum
the total momentum of any isolated system is conserved (one object may gain or lose momentum, but the net total in the system cannot change without interacting with another system)
Conservation of momentum (most common formula)
m?v? + m?v? = m?v? + m?v?
conservative force
a force that conserves mechanical energy (KE, PEg, PEs)
non-conservative force
a force that does not conserve mechanical energy (KE, PEg, PEs)
non-conservative force (main example)
friction
inelastic collision
collision where mechanical energy changes but momentum is still conserved
elastic collision
collision where change in mechanical energy = 0, change in momentum = 0, no change in total KE
explosion
in this type of collision, the objects are together initially and separate after (opposite of inelastic collision)
inelastic collision example
two objects collide into one another and combine (can be treated as one object after this time)
impulse
change in momentum
impulse formula
J = ?p = mv - mv?
impulse performed by a variable force
J = ?F(t)dt
work done by a variable force
W = ?F(x)dx
determining force from potential energies
F = dPE/dx