| vhoidz, I don't know any specific tricks but dimensional analysis may often point you in the right direction when it comes to recalling formulas.
Anyways new question:
Suppose that an electron (charge -e) could orbit a proton (charge +e) in a circular orbit of constant radius R. Assuming that the proton is stationary and only electrostatic forces act on the particles, which of the following represents the kinetic energy of the two-particle system?
let k = 1/(4pi(e0))
a) k(e/R)
b) (k/2)(e^2/R)
c) -(k/2)(e^2/R)
d) k(e^2 / R^2)
e) -k(e^2 / R^2) |