A positive point charge q of mass m is released from rest in a uniform electric field E directed along
the x-axis as in the figure.
(A) What is the acceleration of the positive charge q? Is it in uniform acceleration or not?
(B) What will be the final velocity of the charge after having a displacement x?
(C) What will be the kinetic energy of the charge after it has moved a distance x?
Answer:
initial velocity u=0,
acceleration a=qE/m,
time t=t,
final velocity v=?
by v=u+at, we get
v=0+(
m
qE
)t
orv=
m
qEt
so the final kinetic energy is
K(t)=
2
1
m(
m
qEt
)
2
⇒K(t)=
2m
q
2
E
2
t
2