Two point charges are located on the y-axis as follows: one charge q1 = -1.95 nC located at y= -0.550 m, and a second charge q2 = 3.60 nC at the origin (y=0). What is the magnitude of the total force exerted by these two charges on a third charge q3 = 4.90 nC located at y3 = -0.435 m ?

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".