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## Homework Statement

An electron with speed of [tex]1o^{6} m/s[/tex] enters a [tex]6mT[/tex]

uniform magnetic field that is perpendicular to the velocity of the electron. What is one possible time point after the electron entered the magnetic field that the electron will move along the opposite direction from its final velocity?

## Homework Equations

## The Attempt at a Solution

Since the velocity of the electron and the magnetic field are perpendicular,

[tex]F_{B} = qv_{o}B = ma[/tex]

So,

[tex]a = \frac{qv_{o}B}{m}[/tex]

But,

[tex]v_{f} = 0 = v_{o} + at[/tex]

So,

[tex]t = \frac{-m}{qB}[/tex]

Where am I going wrong?