# Physics of Weighlessness

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Weightlessness occurs when there is no force of support on your body. Free fall is when your body is effectively accelerating downward at the acceleration of gravity; here you are not being supported. The sensation you get from apparent weight (mg- mass times gravity) comes from the support that you feel from the floor or from your seat. Some examples of the sensation of apparent weight occur on a roller-coaster or in an airplane due to the fact that they are accelerating either upward or downward; like going over the very top in a rollercoaster. Weightlessness happens or is met when the downward acceleration of the set is equal to the acceleration of gravity. This is also an example of free falling where you feel this weightlessness (a weigh scale would read zero). As with the aircraft weightlessness occurs any time the aircraft is accelerating downward with an acceleration of 1g. Just as with a ballistic trajectory. Lastly when a person stands on a bathroom scale, it measures the weight because gravity is pulling down on the person. Due to the scale resting on the floor, it pushes up on the person with an equal force and this force gives the weight: Newton’s Third Law- “For every action, there is an opposite, but equal reaction.” Now that we know what weightlessness is and free falling is, let’s move on to how it affects our astronauts. We see them on TV floating in the aircraft and weightlessness looks like fun, it places great demands on an astronaut’s body. Initially, you feel nauseated, dizzy and disoriented. Your head and sinuses swell due to the how the blood is distributed differently through the body and your legs shrink. Long term affects, your muscles weaken and your bones become brittle because they lose calcium. A trip to Mars- three years- would cause the body to lose 10% of bone mass. While in outer space, exercise can help minimize the effects of