Mirror's Edge has it's own PhysX module Installation dating from 2009* separate to the ones included with the latest drivers from which causes issues on more modern GPU's.
Example Here:
(Video Credit to Justin Alex - https://www.youtube.com/channel/UCZyp8Ei8jmDcFd0rKQrt0NQ )

Following this guide should fix most of your issues.
Only Applies to Nvidia Cards AMD cards doesn't support Mirrors edge implementation of PhysX*


*Last I checked

First off make sure you have downloaded the latest Nvidia drivers from.
http://www.nvidia.com/Download/index.aspx?lang=en-us
Or from GeForce Experience

Once installed go to your Mirror's Edge install directory.

For example "C:\Program Files (x86)\Steam\steamapps\common\mirrors edge\" if on Steam.
Once there open the folder called Binaries and delete the following files/folders.

• PhysxLocal folder/directory
  
• PhysXCore.dll
  
• PhysXDevice.dll

Once you've done that launch the game and run through a physics intensive to confirm it's working
Example:
(Video Credit to Justin Alex https://www.youtube.com/channel/UCZyp8Ei8jmDcFd0rKQrt0NQ )

This was posted in the comments to those still having issues after following the previous steps by a user called Crossman
(http://steamproxy.net/profiles/76561198014261711)
I haven't tested this myself personally
Navigate to Program "C:\Program Files (x86)\NVIDIA Corporation\PhysX\"
Copy the following files
cudart32_65 located in \common
-PhysXCore.dll located in \Engine\X.X.X (X.X.X being the latest version for me right now it's 2.8.3
and copy them in to the Mirror's edge Binary Folder

Major credit to Justin Alex for his super well written guide which helped me with updating this guide.

Crossman for his alternate fix (Untested)
(http://steamproxy.net/profiles/76561198014261711)