An ideal, isolated, air-filled parallel-plate capacitor is not ...

[D2AR0N]

An ideal, isolated, air-filled parallel-plate capacitor is not connected to a battery but has equal and opposite charges of 3.9 nC on its plates.
 
  The separation between the plates initially is 1.2 mm, and for this separation the capacitance is 3.1  10-11 F. How much work must be done to pull the plates apart until their separation becomes 7.7 mm? (0 = 8.85  10-12 C2/N  m2 )

Question 2

An object is attached to a vertical spring and bobs up and down between points A and B. Where is the object located when the elastic potential energy of the system object-spring is a maximum?
 
  A) at either A or B
  B) midway between A and B
  C) one-third of the way between A and B
  D) one-fourth of the way between A and B
  E) at none of the above points

[cswans24]

Answer to Question 1

1.3 J

Answer to Question 2

A

[D2AR0N]

Excellent

[raenoj]

Gracias!