trying to game on my lg 27ul500-w and the screen feels laggy or has tearing. i thought it had freesync?

You need to enable both the correct monitor settings and match your graphics card settings.

1. On the monitor, open the On-Screen Menu. Go to Game Adjust. Enable 'AMD Radeon FreeSync™'. This allows the monitor's refresh rate to sync with your GPU's frame rate.
2. Also in Game Adjust, ensure 'Dynamic Action Sync' is On. This minimizes input lag.
3. On your PC, open your graphics card control panel (AMD Radeon Software or NVIDIA Control Panel). For AMD, ensure FreeSync is enabled in the display settings. For NVIDIA, if the monitor is G-SYNC Compatible (check LG's site), enable G-SYNC for windowed and full-screen mode.
4. Make sure you're using a DisplayPort 1.4 cable for the best compatibility. The max refresh rate at 4K is 60Hz on both HDMI and DP for this model.

IF THAT DIDN'T WORK: In the Game Adjust menu, try turning 'Black Stabilizer' on or off. This can affect perceived motion clarity. Also, set the response time to 'Faster' (the 5ms GtG setting).