# Some minor lessons I learnt on applying gravity boundary conditions

To be able to incrementally apply gravity boundary conditions, I tried three different methods to one normal way.

In the ipinit file you would default to set initial displacements to zero and choose gravity vector to be 0,0,9.81 for full gravity.

I then tried { fem def init;r;gravity4905 (having only 0,0,4.905) fem def solv;r;solver fem solv fem def init;r;gravity981 (choosing start from previous sol and set grav to 0,0,9.81) fem def solv;r;solver fem solv } The above way gave a "stiffer" solution in that the body did not deform as much as the default way.

I then tried { fem def init;r;gravity4905 fem def solv;r;solver fem solv fem def init;w;partiallysolved $OldStr = " Specify the gravity vector components \0,0,0\: 0.0000000000000000 -4.9050000000000002 0.0000000000000000" $NewStr = " Specify the gravity vector components \0,0,0\: 0.0000000000000000 -9.8100000000000000 0.0000000000000000" $command = "sed "s/$OldStr/$NewStr/g" gravityPartiallySolved.ipinit > gravityFull.ipinit"; system($command); fem def init;r;gravityFull } and it seemed to work....only derivatives seemed to change. Any other information is welcome.