Particle that moves in an electric and magnetic field

[fight_club_alum]

Homework Statement

A charged particle (m = 5.0 g, q = –70 μC) moves horizontally at a constant speed of
30 km/s in a region where the free fall gravitational acceleration is 9.8 m/s2 downward,
the electric field is 700 N/C upward, and the magnetic field is perpendicular to the
velocity of the particle. What is the magnitude of the magnetic field in this region?
a . 47 mT <-- answer
b. zero
c. 23 mT
d. 35 mT
e. 12 mT

Relevant Equations

F = ma
q . v . b . sin(theta) = F

m = 0.005
q = -70 x 10^-6 c
v = 30,000 m/s
Since there is no movement vertically Fb = Mg
So,
q . V . B = mg
So,
(70 x `10^-6) . (30,000) . B = (0.005) . (9.8)
So,
B = 0.0233333 or ~ 23 MT

 

[Orodruin]

What about the force from the electric field?

 

[Orodruin]

23 MT

Also:
You mean 23 mT. 23 MT is a humongous magnetic field strength...

 

[fight_club_alum]

Thank you for replying
Can I please know how can I take it into account?

 

[Orodruin]

What is the force due to an electric field on a charged particle?

 

[fight_club_alum]

What is the force due to an electric field on a charged particle?

It seems that I've been studying for so long now that I couldn't notice what I first learned in this course

Thank you so much for pointing out my obvious mistake

 

[Orodruin]

Sometimes you don’t see the forest because of all the trees...