Please help me with this

[Britney2]

A charged particle that moves with the speed v=8x10(7) goes in a magnetic field where B=0.7 T (B is the induction) and it makes an angle λ=45◦ with force lines. How is the specific charge(q/m) if the radius is R=4 cm?
(qvb=mv2/R qvb is the formula of the Lorenc force and mv2/R is the centripetal.)

 

[rock.freak667]

The force exerted on the charged particle at an angle $\theta$ to a magnetic field of flux density,B, and moving with a velocity,v, provides the centripetal force to keep it moving a circular path.

So that

$$BQvsin\theta=\frac{mv^2}{r}$$

Which is the formula you posted in a sense...