Physics help involving electric field charge

[aaronmilk3]

A proton orbits just at the surface of a charged sphere of radius 0.83 cm. If the speed of the proton is 4.96 X105 m/s, what is the charge on the sphere?


proton mass = 1.67e-27
proton charge = 1.6e-19
Radius = .0083 meters

I thought maybe F = (mv²)/r
((1.67e-27)(4.96e5)²)/.0083

Then E=F/q

But this doesn't seem to be right.

Any help would be appreciated. I have tried it a couple times with no luck. Just need to get in the right direction. Thank you in advance!

 

[ehild]

What do you mean on E=F/q? What are E and q?

ehild

 

[aaronmilk3]

E = electric field
q = the charge
F = electric force

 

[ehild]

You need the charge of the sphere. If E is the electric field strength at the place of the proton, the electric force on the proton is F=eE where e is the elementary charge. How are the electric force and the centripetal force related? How do you get the electric field of the sphere?

ehild

 

[aaronmilk3]

Thanks. I figured it out.