# Help on a physic 30 question

## Homework Statement

Hello, i am in physics 30 and my teacher gave our class a worksheet for homework and I am stuck on the last question. Could anyone help me out please? Thanks.

Here is the question: Show that the units of 2$$\pi$$m/ qB are equivalent to seconds.

How can I get the unit for time (s) from that? what do I have to show?

## The Attempt at a Solution

I tried using Fc = Fm but I dont get how 2$$\pi$$ is used in the equation? Or does it even have an effect and is there just as a constant with no units.

Last edited:

Welcome dulask Start by writing out all of the units for each symbol in the expression
$$\frac{2\pi m}{qB}$$

I do not know what any of them are just by looking at them. I could venture a guess, but I rather not

Pengwuino
Gold Member
This problem is kinda annoying as B is in Tesla, q is a charge, m is a mass right? Well here's a nice little trick:

Do you know the Lorentz force law? F = q(E + v x B)? On one side is a force, something with units you should know and are far more comfortable with. On the other side, it has these crazy coulomb and tesla units! I'll assume you may not have gone over it but basically, dimensionally F = qvB! From there you should be able to figure it out.