An electric dipole with dipole moment = (3.04 + 4.19 )(1.27 × 10-30 C·m) is in an electric field = (4035 N/C). (a) What is the potential energy of the electric dipole? (b) What is the magnitude of torque acting on it? (c) If an external agent turns the dipole until its electric dipole moment is = (-4.19 + 3.04)(1.27 × 10-30 C·m), how much work is done by the agent?

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".