When useDamping is false (the default), this is absolute loss of velocity due to movement, in pixels per second squared.
When useDamping is true, this is a damping multiplier between 0 and 1.
A value of 0 means the Body stops instantly.
A value of 0.01 mean the Body keeps 1% of its velocity per second, losing 99%.
A value of 0.1 means the Body keeps 10% of its velocity per second, losing 90%.
A value of 1 means the Body loses no velocity.
You can use very small values (e.g., 0.001) to stop the Body quickly.
The x and y components are applied separately.
Drag is applied only when acceleration is zero.