Finding Magnetic Field of Alpha Particle in a Circle

[howt]

Homework Statement

An alpha particle is moving at constant speed in a circle, perpendicular to a uniform magnetic field, making a revolution every 60 nanoseconds.
Its speed is non-relativistic

What is the numerical magnitude of the magnetic field in T ?

Homework Equations

alpha particle (2 protons + 2 neutrons)

We have here T= 2(pi)m / qB

in which
m=Mass (alpha particle= 6.64*10^-27) kg
q=Charge = 2(1.6*10^-19) C
T= (60*10^-9) s

The Attempt at a Solution

This should be just plugging in, I got 2.1729, yet it is wrong...
Why?

 

[rl.bhat]

What is the radius of the circle?

 

[howt]

it is not given...

I don't think we need it to solve the question
The formula of it doesn't involve any radius...

 

[rl.bhat]

it is not given...

I don't think we need it to solve the question
The formula of it doesn't involve any radius...

When the alpha particle is moving ina circle, what is the force acting on it?
What is the force on alpha particle due to the magnetic field?

 

[howt]

The Centripetal force is going to equal the magnetic force.

Note that w = v/r

Centripetal force , F=m v^2 /r..
=m r w^2

And the magnetic force on the alpha particle is, F = B q v
= B q w r

m r w^2 = B q w r
m w = B q

in which w= 2(pi) / T

Thus T= 2(pi)m / qB

 

[rl.bhat]

Your answer appears to be correct.

 

[howt]

Thanks, the problem might be those constant...

Side Note: I just realize I got a typo on the topic... crap