# I know im forgetting something simple

1. Mar 1, 2005

### bemigh

Once again, hello...
Alright, i know im forgetting something simple...

A singly-charged positive ion of mass 2.50 ´ 10–26 kg, initially at rest, is accelerated through a potential difference of magnitude 2.50 ´ 102 V.

(a) Calculate the speed of the ion after passing through this potential difference.

(b) The ion then enters a region of uniform magnetic field of magnitude 0.500 T. The direction of the magnetic field is perpendicular to the ion’s velocity. Calculate the radius of the path of the ion in the field.

Now, i can solve this... however, im stumped by something... How can i find the velocity of the particle after it leaves the potential difference... I would need q of the particle, allowing me to use K=qV, i know everything but q... is their another way of solving for the velocity??
Cheers

2. Mar 1, 2005

### StatusX

No, you absolutely need q. How else could you calculate the electric force? since this is a singly charged ion, q is the basic charge e, 1.6x10^-19 C.