If you’ve ever loaded your worldly possessions into a truck in preparation for a move, you have firsthand experience with the concept of “tippability.” Load all your heaviest stuff on top of your lightest stuff and, if you manage not to crush the lower layer, you’ll have a seriously unbalanced load — the sort of load that will cause your truck to land on its side as it make its first serious turn. Fail to fill the truck completely and instead leave the load to move freely within the truck and you can easily find yourself in the same predicament. The question is: WHY?
The answer is: The Center of Gravity. The center of gravity for objects at the earth’s surface is the point at which all forces net to zero. If you tack something to the wall with one tack, you know you have to get that tack just right. If you don’t, the object will tilt or spin on the tack. The reason it will do that is because the load is unbalanced. You must get the load balanced just right – you must tack the piece through the center of gravity – if you are to be successful.
If the guy in this image were not balanced properly, he would take a tumble. It is only because he has found the center of gravity that he is able to maintain this position. If you were to tug hard on his left leg to simulate the movement of a heavy piece of furniture, he would quickly fall over. Likewise if you were to apply a force to any other area of his body. As long as he is in balance, he will stay in this position. Cause him to be unbalanced and he will tip.
Imagine the Sewol Ferry as the truck or the man in the image. Now imagine what it would take to make the ferry “tippable.”