It isn't open long enough for you to get through Shoot a portal of the other color onto the wall behind the little door.
Go into that side room and create a portal on the wall in here. The little side room with a button in it. Ride the platform, crouching to pass under the pneumatic thing, hop onto the grating, and continue riding the platform until you get to On the angled piece of wall that does have a pellet bouncing on it. Put a portal on the angled piece of wall that doesn't have a pellet bouncing on it, then put another portal Test Chamber 17 - The Weighted Companion Cube will Never Threaten to Stab You.Test Chamber 15 - Cake and Grief Counseling.Test Chamber 14 - You are an Excellent Test Subject.Test Chamber 13 - A very, VERY long time.Test Chamber 12 - Fling Yourself into Space.
