Question

An electron that has a horizontal initial speed of 4.50 106 m/senters a region that has an electric field of 120 V/m pointingvertically upward.
(a)How long does the electron take to travel 20 cm in thehorizontal direction?
____7.18E6_________s

(b) In this same time, what is the vertical displacement of theelectron? Treat up as positive.
________________cm

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I am having trouble the second portion of this problem. Heres mywork so far:

I calculated the force by F= (1.60E-19J)(120 V/m)=1.92E-17N

Then I calculated the acceleration: a= (1.92E-17N)/(9.11E-31kg)=2.1E13 m/s2 upward

Using the equation: Y=Voyt + (1/2)ayt^2

Y= (0) + .5(2.1E13 m/s^2)(4.44E-8)^2

Answer: 2.6 cm is wrong