A point charge, q = +4.7 uC, is
ed at each corner of an equilateral triangle with
des 0.21 m in length. (a) What is the magnitude of the
Sectric field at the midpoint of any of the three sides of
the triangle? (b) Is the magnitude of the electric field
at the center of the triangle greater than, less than, or
the same as the magnitude at the midpoint of a side?
Explain.

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".