Phy53 Lecture Dr. Brown 21 Sep 2010
quiz hint -- similar to two hwk problems ;) continue your good work on recitation problems
extend work and energy theory -- in particular --rate of work = Power
then derive conservation of energy -- conservative/non-conservative forces and potential energy
Total power = \vec{F} \cdot \vec{v}
define conservative force --> path independent : \oint_c \vec{F_x} d\vec{x} = 0 for all closed paths c
rearranges the Work - K-Energy theorem and defines potential energy
Note that if only conserv forces are acting, then the sum of work function and the KE at some point in space is a constant -- define mechanical energy
what if non-conserv forces? --> W_{nc} = \Delta{E_{mech}} generalized work-mechanical energy thm
examples:
find speed of block, m when it slides down a frictionless incline ( \theta ) a distance L [normal force does no work because it is perpend. to motion]
same but on frictionless ski slope
ball on loop -- assuming frictionless sliding! [so we can ingnore the KE of rotation]
mass on spring -- potential energy for spring