In dance if you are posing you will not move until you force yourself to do so. If you are in a leap you will stay in the air for only a short amount of time because air resistance and gravity are working against you.
If you are in a turn, you need to have equilibrium to make sure you can maintain balance. If you do a needle you need to have inertia to remain steady and make sure your body is unchanging.
Whenever a dancer does a leap they apply a downward force on the stage and the stage applies an equal force up on the dancer to leave the stage to leap into the air.