MOMENTUM & INERTIA
MOMENTUM: “Generally, we consider momentum as the motion of a ship at the time we no longer want it, especially when we have taken action to obtain the opposite effect. ... Momentum is the quality of motion measured by the product of mass & velocity.”
INERTIA: Inertia is the quality of motion that causes a ship to resist a change in motion. “A force exerted on a ship will result in motion after inertia has been overcome.” Hooyer - Behavior and Handling of Ships
Notes:
THE FIRST CONCEPT TO KEEP IN MIND IS THAT OF MOMENTUM AND INERTIA. ALL SHIPS EXPERIENCE MOMENTUM AND INERTIA. ONCE YOU LEARN THE HANDLING CHARACTERISTICS PARTICULAR TO YOUR SHIP YOU CAN USE THESE PHENOMENA TO YOUR ADVANTAGE OR AT LEAST ACT TO COUNTER THEM.
KEEP IN MIND IN ORDER TO CHANGE A SHIP’S MOMENTUM, A FORCE HAS TO BE APPLIED TO OVERCOME INERTIA. THIS IS NOT INSTANTANEOUS.
IF YOU ARE GOING TO A LARGE SHIP, GREATER FORCE WILL BE REQUIRED TO OVERCOME THE INERTIA. TYPICALLY, HOWEVER, LARGE SHIPS HAVE A LOWER HORSE POWER TO TONNAGE RATIO. TO CHANGE MOMENTUM LARGER BELL CHANGES AND EARLY ACTION WILL BE REQUIRED.
THE ADVENT OF MANY OF OUR MODERN CONTROL SYSTEMS SUCH AS CPP AND GAS TURBINE ENGINES ALLOW US TO MORE EASILY COUNTER ACT THESE FORCES WHEN MANEUVERING.