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## Homework Statement

An alpha particle (helium nucleus, charge +2

*e*) starts from rest and travels a distance of 2.5 cm under the influence of a uniform electric field of magnitude 12.5 kV/m. What is the final kinetic energy of the alpha particle?

## Homework Equations

U = 1/2 QV = 1/2 C(V^2) = (Q^2)/2C

Q = CV

C = (Eo A)/d

where U = potential energy, Q = charge, C= capacitance, A= area, d = distance, and V = potential difference

## The Attempt at a Solution

I tried using U = 1/2 QV by calculating that the charge is 2 times the constant charge of an electron (1.602x10^-19) and used 12.5 kv/m as V (but changed it back to just volts.

U = 0.5 (3.204x10^-19) (12500 v/m)

U = 2.0025x10^-15

But this is wrong. Also, in a practice version of the problem it said that given magnitude = 18.5 kv/m and distance = 1.6 cm the answer would be 9.48x10^-17.

Any help with this problem would be greatly appreciated.