Stuck on "Our Benefactors"

[Armed Partisan]

Have been using the G-gun a lot. At one point I am in a long hall like complex with a strider and 4-5 enemy at the other end. There are personal tranport units along the walls and laying about. There are two strands of energy balls running up into the sky and out of sight. After I destroy the strider and kill the Combine troops Administrator comes on on a large video screen on the far wall behind where the strider was, saying something like 'look what youre throwing away'. There is one room to the left of the video screen with a force field over it. There appears to be an energy core just inside with a red buttom or camera near it. I cant tell where to go next. Seem trapped.. . Please help!
AP

 

[Analogy]

How have you opened up all of the other force fields that you've had to go through?

Spoiler

Draw all of the energy balls out of the core with the grav gun

 

[Computer5k]

I think you have to use the manipulator to pull the energy core out.

 

[Jordie]

Use grav gun to suck out all the energy balls from the core behind the shield.