How do lifejackets make you float?

Answer 1

Floating in any liquid or gas does not depend upon weight as many might think. Instead it depends on a property called density, calculated as mass divided by volume.

All matter has mass (the amount of stuff in it) and volume (the amount of space that stuff takes up). water and people have about the same density, because we are made up mostly of water. Many people will float in the water without trying, some people will sink, and it all depends of that value of density.

Life jackets, by mass (the foam), take up large portion of volume (space) compared to a human. So putting it on cheats your bodys density and greatly makes you less dense allowing you to float.

Answer 2

Life jackets or rafts are filled with air and operate with the principle of buoyancy. In effect, because of the pressure difference between the fluid from below and the pressure exerted from above, the raft or jacket floats.

Answer 3

Things float by displacing more water than they weigh. So, in your body, gas weighs much less than water. The air you breath and the intestinal gas in your body helps you float. Some fat deposits can also weigh less than water and often do weigh less than salt water. If you are very lean and breath out all your air, you are more likely to sink. If you are obese you are less likely to sink. Since salt water is denser (heavier by volume) than fresh water, you float better in it.

Answer 4

Most lifejackets contain a material that is more bouyant than water, so when you have one on this bouancy holds your head above the water.