Challenge: Sinking logs
Create a fluid resistance force to slow the logs down as they sink.

Add fluid resistance!

Hint

if () {
var = ;
logs[i].applyForce();
}

These logs should be decelerating when they hit the water, from the fluid resistance, but they're bouncing
back up! Fix that by calculating and applying the drag force at the appropriate time, using methods from
the Liquid object.