Buoyancy

Ships are designed to float. How do they? How is it possible that something so large can float on the water? The answer is buoyancy, the ability to float. To really understand this however, you must learn about buoyant force (Jones).  As you can see the weight of the object and the amount of displaced liquid is equal, therefore the object floats.

You have most definitely experienced buoyant force. You know that when you pick up an object under water, it is much lighter then it is above water. Buoyant force is the upward force water and other liquids exert on submerged objects. The buoyant force isn't the only underwater force. As you probably know, the deeper you get, the more pressure is pushing on you from all directions (Jones). "The pressure on the bottom of a submerged object is greater than the pressure on top," (Jones 83). The reason is because the net force is greater from the bottom because of buoyant force combining with the water pressure. Buoyant force is found by using Archimedes' Principle. This states that the buoyant force acting on an object is equal to the weight of the displaced fluid (Jones).



As an example, if a weight that weighs 7N is dropped into water and a weight equal to 3N of water is displaced, the rock will sink and will feel like it only weighs 4N. However, if a rock weighs only 1N and it displaces 2N or more of water, it will float. As you can see, this is greatly determined by density.

(Buoyant Force) ||= Sink or Float ||
 * = Weight of Object ||= Displaced Fluid
 * = 1N ||= 3N ||= Float ||
 * = 2N ||= 3.5N ||= Float ||
 * = 3N ||= 4N ||= Float ||
 * = 4N ||= 4.5N ||= Float ||
 * = <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">5N ||= <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">5N ||= <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">Float ||
 * = <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">6N ||= <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">5.5N ||= <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">Sink ||
 * = <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">7N ||= <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">6N ||= <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 12pt; text-align: center;">Sink ||

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By Brian_L.13 and brentc121