A Positron has the same mass, but opposite charge to an electron. A Positron and electron are orbiting around each other separated by 1μm, in a stable circular orbit about their centre of mass, as a result of electrostatic attraction. Calculate the period

State Coulomb's law:F=(1/4πE0 )(qQ/d2)Since the distance separating the charges is twice the radius of the orbit relabel d to 2r and the charges are equal and opposite:F= -(1/16πƐ0 )(q/r)2Notice that this is simple circular motion so we can use the force to relate these two concepts in an equation (here we can ignore the negative since it is present in the previous equation by convention to show that the force is attractive, in circular motion an inwards force is considered positive):mw2r = (1/16πƐ0 )(q/r)2w = sqrt(1/mr3πƐ0 )(q/4)Knowing that T = 2π/w, obtain:T= sqrt(mr3 πƐ0)*(8π/q)Put all the numbers in on a calculator to get the final answer:2.8 x 10-10s (2 s.f.)

JB
Answered by John-Joseph B. Physics tutor

2027 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

calculate the resistivity in a 1.2m length of cylindrical wire with radius 1cm. The resistance of the wire is 0.01 kilo Ohms


Use band theory to explain the changes in the resistance of an intrinsic semiconductor as temper changes.


What is EMF? How do we test for it?


A child is standing on a walkway that is moving at 2 metres per second and decides to turn around and walk back to the start at 2 metres per second. Explain why the child cannot reach the start of the walkway at this speed.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning