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Course 3 of 7

Portal 2: Mass and Velocity walkthrough

Momentum chambers: flings through portals and aerial faith plates.

  • About 15–20 min in the videos
  • 8 parts · 27 steps

Steps from 15 text guides, 2 videos to watch · checked Oct 18, 2026

0 of 8 done
Video: AnthyDaBeist on YouTube. Loads from youtube-nocookie.com only when you press play.

What each player can do here

P1 · Atlas
  • Atlas carries a portal gun with a pair of blue and purple portals; the two pairs work together, so either of you can step through the other's portals.
P2 · P-body
  • P-body carries a portal gun with a pair of orange and red portals; the two pairs work together, so either of you can step through the other's portals.

If your skill levels differ: Both bots carry the same kind of portal gun. Pings let you mark spots and time moves without talking, and failing costs little because a destroyed bot is rebuilt within seconds. How to split the roles

Flings

Part 1 of 8. Fling across rooms with partner portals, then seat a ball in the receptacle.

  1. BothEach partner's floor portal flings the other across, so every fling needs both players.
  2. AtlasAtlas portals up to the higher ledge, then jumps into the floor portal P-body made to reach the upper ledge.
  3. P-bodyP-body portals to the platform Atlas used first, then jumps into a floor portal to reach the lower ledge.
  4. BothThe buttons drop a ball; one of you sets it in the receptacle and the exit opens.

Infinifling

Part 2 of 8. Use infinite fall loops and angled panels to fling partners across the goo.

  1. AtlasAtlas walks past the pedestal button and waits in the alcove for the partner to fling across.
  2. P-bodyP-body sets an orange portal above the partner and a red one below to create an infinite fall.
  3. P-bodyP-body presses the pedestal button to move the wall, then fires an orange portal at the angled panel.
  4. BothThen swap jobs to bring P-body across; the pedestal button for that is past the goo.

Where people tend to fall

  • The goo pool under the fling route is hazardous to a missed catch.

Team Retrieval

Part 3 of 8. Build speed with portal loops, fling across the goo, then deliver the ball to the receptacle.

  1. P-bodyP-body sets an infinite fall above and below, then shoots a portal onto the high panel to fling Atlas across.
  2. AtlasAtlas presses the pedestal button to dispense a ball, picks it up, and holds it high on the ledge.
  3. P-bodyP-body takes the ball from Atlas and walks through Atlas's portals to put it in the receptacle.
  4. BothThe top floor holds the goo pool and an Edgeless Safety Cube.single source

Vertical Flings

Part 4 of 8. Oscillate between two shafts to hit both pedestal buttons and release four balls.

  1. P-bodyP-body sets an endless fall loop, then places portals on the bottom of both shafts for Atlas to oscillate between.
  2. AtlasAtlas presses the pedestal button on each upward pass through the shafts and keeps trying until both are hit.
  3. BothOnce both buttons are hit close together, four balls drop, and one partner seats a ball on the receptacle.

Where people tend to fall

  • The quick portal swap for the achievement may be more difficult using a controller.

Catapults

Part 5 of 8. Launch through faith plates, carry a cube to the button, then reach the dual door together.

  1. AtlasAtlas sets a portal on the angled panel and one above the faith plate, then catches the cube mid-air.
  2. P-bodyP-body launches through the fizzler, takes the cube from Atlas at the ledge, and places it on the button.
  3. AtlasAtlas waits in the revealed alcove without touching the fizzler while P-body finishes the route.

Multifling

Part 6 of 8. Ferry cubes through portal chains with faith plates, then drop a cube on the receptacle.

  1. AtlasAtlas walks through the fizzler into the far half, then portals onto the two angled panels there.
  2. AtlasAtlas grabs the cube in mid-air, walks it to the platform and sets it in the receptacle, which opens the exit.

Fling Crushers

Part 7 of 8. Time faith plates, raise the lift with the pivot cube beam, then run the cube to the door.

  1. BothEach partner takes a faith plate and a button, then both step on them together using the ping tool timer.
  2. P-bodyP-body takes the pivot cube down the hallway to the laser and aims it through a portal to raise Atlas's lift.
  3. AtlasOnce the lift stops, Atlas drops into the floor portal, flies into the faith plate and lands next to a button.
  4. P-bodyP-body drops the cube on the faith plate near the door and runs through before the door closes.

Where people tend to fall

  • The door closes quickly after the cube hits the button.

Industrial Fan

Part 8 of 8. Redirect the laser beam into the receiver to stop the fan, then put the disc in the player.

  1. AtlasAtlas shoots a blue portal at the 01 panel and a purple portal on the floor, then jumps into the purple one to reach the button.
  2. AtlasAtlas jumps into the purple portal to cross the room, then places a portal under and a little left of the clock.
  3. BothEach of you takes a switch beside the door and you throw them together on the ping-tool timer; then one of you puts the disc in the player.

Extras and notes

  • Four Ring Circus (Vertical Flings): one bot keeps falling back and forth through the shafts while the partner moves the portals so the bot never lands; either bot can earn it.
  • Dance Gesture (Catapults). Unlocked for both players once both partners reach the dual door.
  • Iron Grip (Multifling). Both players earn it if no cube is lost in the goo on the first attempt.
  • Confidence Building (Industrial Fan). Completing all test chambers in Course 02 unlocks this achievement.
Sources (17)

Steps compiled from 15 text guides, checked Oct 18, 2026, and written in our own words. The videos are there to watch each part; they are not counted as sources for the steps. We did not play the game for this guide. A step marked “single source” rests on one guide so far.