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Throughout space there is a uniform electric field in the -y direction of strength E = 540 N/C. There is no gravity. At t = 0, a particle with mass m = 3 g and charge q = -17 µC is at the origin moving with a velocity v0 = 25 m/s at an angle θ = 25° above the x-axis.

(a) What is the magnitude of the force acting on this particle?

F = 0.00918N

(b) At t = 6.5 s, what are the x- and y-coordinates of the position of the particle?

x = ? y = ?

HELP: Recall and apply the kinematic expressions for 2-D projectile motion from mechanics.

E = F/Q = (KQ)/r^2

Range = (vo^2*sin(2Θ))/g

Trajectory = x*tan(Θ)-(1/2)((g*x^2)/(vo^2*cos^2(Θ))

v = vo+at

x = xo + v0t+(1/2)at^2

v^2-vo^2 = 2a(x-xo)

Ok pt a.) was really easy but I'm completely stuck on part b. It says to use kinematics equations but I don't see how that can work. We're not given acceleration and we're told gravity is not acting on the particle, and we don't know the speed at t=6.5s. I thought maybe I could set the force from pt a equal to m*a and that gave me 3.06 but the coordinates I got were not correct. Am I suppose to assume that the acceleration is zero since the electric force field is constant?

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# Homework Help: Electric Fields Question- Uniform Field

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