Speed of an Electron and the Magnetic field

[mlsohani]

Homework Statement

An electron with kinetic energy 1.60 keV circles in a plane perpendicular to a uniform magnetic field. The orbit radius is 24.0 cm.
a Find the speed of the electron.
b Find the Magnetic Field

Homework Equations

k=1/(2mv^2)
B=mvqr

The Attempt at a Solution

I first converted keV to Joules which came out to be 2.5635 e-16 J

I then made the equation to solve for v : v=sqrt(1/2mk)

But I came out with the velocity being e22 4.627 km/s which is not right

PLease help!

 

[alphysicist]

Hi mlshani,

Homework Statement

An electron with kinetic energy 1.60 keV circles in a plane perpendicular to a uniform magnetic field. The orbit radius is 24.0 cm.
a Find the speed of the electron.
b Find the Magnetic Field

Homework Equations

k=1/(2mv^2)

This equation does not look right to me; do you see what it needs to be?

 

[mlsohani]

No I thought that was the equation, at least that is the one on my physics book?
Is there another equation to find the speed of an electron?

 

[Volcano]

(mV^2)/2

 

[mlsohani]

Thank you!

I can't believe I saw that equation as having everything in the denominator!

Thank you!