Manchester Memoirs, Vol. hit. (191 3), No. 4. 



To calculate the mean kinetic energy (>) of thi 

 motion we have 



-^/'i/"V. ^^ 



/TfJ 



dt 



■ (4) 



/ being the moment of inertia of the magnet and (o its 

 angular velocity. Also, as before, 



+ A'sin6> = 



and therefore 



dB 



e\i 



dt ^'^^l - 3/ 

 On substituting in equation (4) we get 

 e = 2 ir/{ j "(sin^^ - sin^^)" * ^0} " ' [" (sin^ ^ - siir ^^^dQ. 



Y/(/i 



iAY 



2A^/(/, 



\f^ ) 



^A/| — - I - cosci j- 



^s^ 



