Proton speed needed to circle the earth

[mba444]

Homework Statement

Assume that Earth’s magnetic field is every-
where perpendicular to the path of a proton
and that Earth’s magnetic field has an inten-
sity of 4.19 × 10−8 T.
What speed would a proton need to achieve
in order to circle Earth 1550.0 km above the
magnetic equator?
Answer in units of m/s.

Homework Equations

r=m*v/Q*B
r=(r Earth + r given in the question )

The Attempt at a Solution

i solved for v but I am not sure if what I am doing is correct

 

[rl.bhat]

You are in right track.

 

[mba444]

thanX