Cracking the SAT Physics Subject Test

through the equilibrium position, O, this energy has been converted entirely to

kinetic. By setting mv^2 equal to kd^2 , we find that

70. D Because the particle travels in a circular path with constant kinetic energy
    (which implies constant speed), the net force on the particle is the centripetal
    force.


71. A The change in the electrical potential energy as a charge q moves from
    position X to position Z is equal to q times the difference in potential
    between the points: ΔPE = qV = qΔφ = q(φZ − φX). Because positions X and
    Z are equidistant from the source charge (+Q), the potentials at these
    locations are the same. Since Δφ = 0, there is no change in potential energy,
    so the work done by the electric field is also zero.


72. E The electric field strength is given by E =. Therefore