The electric potential along the x-axis is described by for

PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

The electric potential along the x-axis is described by

V(x)=2.0\,\text{V}+3.0\,\text{V/m}\,(x)

for

0\le x\le4.0\,\text{m}

. A singly charged potassium ion

\text{K}^+

(charge

+e

) enters the region at

x=0

with a speed of

1.0\times10^{3}\,\text{m/s}

directed toward

+x

. Neglecting all forces except the electric force, which of the following best describes the change in the ion’s kinetic energy after it reaches

x=4.0\,\text{m}

? (a) It increases by

12\,\text{eV}

. (b) It decreases by

14\,\text{eV}

. (c) It decreases by

12\,\text{eV}

. (d) It remains the same because the electric force does no net work.