phys 110 final study guide - CHP 10 energy concepts(Diagram...

CHP 10 // energy concepts: (Diagram) Energy into system  [total energy E = K + U]  Energy out of system // Conservation law for free-fall motion : K
f
+ U
gf
= K
i
+ U
gi
Launching pebble example // Kinetic and Potential energy: scalar, not vector; Units  1 joule = 1 J = 1 kgm 2 s 2 // Kinetic  K = ½mv 2 ; Energy of motion; Depends on
object’s speed; Always positive // Gravitational Potential  U
g
= mgy; Energy of position; Depends on object’s position // complex probs : if surface is curved, can subdivide
surface into many small straight-line segments; K
f
+ U
gf
= K
i
+ U
gi
; for ANY frictionless surface; particle’s speed changes as it changes position // conservation of E
mech
: E
mech
=
K + U; Sum remains constant // Basic Energy Model: 3 hypotheses 1) K is associated w/motion of particle and U is associated w/position 2) K can be transformed to U (vice
versa) 3) Under some circumstances, E
mech
= K + U is conserved // Prob-solving strategy: Conservation of E
mech :
Model choose system w/o friction or other losses of E
mech
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