Equations

information

units

F = k(q_{1}q_{2 })/r^{2} 
vector: magnitude, direction, components (resultant) ^{+ forces represent repulsive forces between two charges} 
N

E = kQ/r^{2} 
vector: magnitude, direction, components (resultant) ^{+ fields represent fields around positive charges} 
N/C
V/m

where k = 9 x 10^{9} N m^{2}/C^{2} 
Coulomb's constant

N m^{2}/C^{2}

F = qE

vector: magnitude, direction, components (resultant) ^{
+ forces represents forces whose direction in the same direction as the field
line
} 
N

V_{abs} = kQ/r

scalar: magnitude only
^{+ equipotential surfaces surround positive charges} 
J/C

EPE = qΔV_{abs} 
scalar: magnitude only
^{+ EPE signifies that the charge has gained electric potential energy} 
J

EPE_{sys} = Σk (q_{i}q_{j} / r_{ij})

scalar: magnitude only
Remember that this is the SUM OF THE POTENTIAL ENERGY OF EACH PAIR of charges

J

W_{done by external agent }= qΔV

scalar: magnitude only
Remember that the absolute potential at infinity is defined to be zero.

J

W_{done by field }= ΔEPE

scalar: magnitude only
Remember that + charges move to points of lower electric potential when moved along
electric field lines, therefore they lose EPE. Consequently, when the field
does positive work on a charge, (W = Fs cos θ where
θ = 0º) the charge loses EPE and gains KE

J

previous material:
kinematics equations
(accelerated motion)
R = v_{H}t
net F = ma
W = Fs cos θ
KE = ½ mv^{2}
conservation of energy

Remember to use H  V charts when analyzing 2dimensional motion
Remember your graph shapes for s vs t and
v vs t Remember that projectiles have a parabolic trajectory when they experience
accelerated motion in one dimension and constant velocity in another

