Finding acceleration of 9N block relative to pulley

[pcpssam]

for part(i) the answer is g/4 + g/2 = 3g/4 ms^-2
how to calculate the acceleration of the 9N blcok relative to the small pulley to be g/4??
Did I miss something?
thank you so much!

 

[SammyS]

[IMG ]http://upload.lsforum.net/users/public/v48021i223.png[/PLAIN]

for part(i) the answer is g/4 + g/2 = 3g/4 ms^-2
how to calculate the acceleration of the 9N block relative to the small pulley to be g/4??
Did I miss something?
thank you so much!

The small pulley has rotational inertia. Therefore, the tension on the string supporting the 3N particle is different than tension on the string supporting the 9N particle.