The dance of Shiva..

Inertia means both Idle (systems at rest continue to be at rest) and Ever Active (those that move continue to move).

Vaikuntha comes from Vi+Kuntha. Kuntha means inert/idle/dull. Vi-Kuntha could mean the opposite Active/Sharp etc.. But vi prefix in sanskrit is similar to dis/de in English. It negates at time (dis-appear), specifies at times (vi-jnana, disseminate) and intensifies (dis-gruntled) at times. So Vi-Kuntha could mean inert/dull also.

Thus it is both Active and Inert, which is what is Inertia. That's why Vishnu is mAdhava (Madhu) and madhu-sudhana both.

-TBT