What is the orbital frequency of an electron and positron 2.00nm apart?

AI Thread Summary
The discussion focuses on calculating the orbital frequency of an electron and a positron that are 2.00 nm apart. Participants clarify that the system should be analyzed using Newton's laws rather than torque, emphasizing the importance of understanding circular motion. By applying the net force equation Fnet = mv^2/r, one can derive the relationship between radius and velocity. This leads to determining the orbital period, which is essential for calculating frequency as the reciprocal of the period. The conversation highlights the need for a correct approach to solve the problem effectively.
imafam
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A positron is an elementary particle identical to an electron except that its charge is . An electron and a positron can rotate about their center of mass as if they were a dumbbell connected by a massless rod. What is the orbital frequency for an electron and a positron 2.00nm apart?

My Approach:
I treated the electron and positron as a system with a torque.
I found that the torque = pEsintheta = qsEsintheta = (1.60*10^-19)(2*10^-9)(1.94*10^9)
but I don't know theta
HELP!
 
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Hi imafam,

imafam said:
A positron is an elementary particle identical to an electron except that its charge is . An electron and a positron can rotate about their center of mass as if they were a dumbbell connected by a massless rod. What is the orbital frequency for an electron and a positron 2.00nm apart?

My Approach:
I treated the electron and positron as a system with a torque.
I found that the torque = pEsintheta

This is the formula for the torque on a dipole in an external field E, which is not what you have here.

Instead, think in terms of Newton's law. Draw a force diagram for one of the particles. Also, the particles are going in a circular path; what do you know that is true about circular motion, that you can use here in Newton's law Fnet=ma?
 
That Fnet = mv^2/r
alphysicist said:
Hi imafam,



This is the formula for the torque on a dipole in an external field E, which is not what you have here.

Instead, think in terms of Newton's law. Draw a force diagram for one of the particles. Also, the particles are going in a circular path; what do you know that is true about circular motion, that you can use here in Newton's law Fnet=ma?
 
imafam said:
That Fnet = mv^2/r

That's right; once you plug in what Fnet is for this case, you'll have an equation with r and v in it.

From that, you can determine the period of the orbit, which is just how long it takes for the particle to go in a complete circle. And then the frequency is just the reciprocal of the period.
 

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