Question

Thank you !

At some instant the velocity components of an electron moving between two charged parallel plates are vx = 1.3 105 m/s and vy = 3.6 103 m/s. Suppose that the electric field between the plates is given by E = (120 N/C) j.
(a) What is the electron's acceleration in the field?
m/s2 j
(b) What is the electron's velocity when its x coordinate has changed by 4.8 cm?
m/s i + m/s j


(a) The acceleration can only be in the direction between the plates, and equals
a = F/m, where the force is F = e E
e is the electron charge.
a = (e/m) E.
m is the mass of an electron.
Look up m and e and solve for a.

(b) The velocity component parallel to the plates remains constant. You don't say whether the plates are oriented in the x or y direction; that needs to be specified. The velocity component between the plates changes from v1 to v2 according to
(1/2)(v2^2 - v1^2) = e E *(change in x)
In your case the change in x is 0.048 m.

Thanx!!!!

I left out the mass in one equation. it should read:
The velocity component between the plates changes from v1 to v2 according to
(1/2)(v2^2 - v1^2) = a *(change in x)

= (e/m) E *(change in x)