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Zero gravity in space: A look at the experience of Astronauts


A frequent misunderstanding by many people today is that astronauts experience zero gravity especially when referring to astronauts in space. Many believe astronauts are weightless in space and that justifies their ability to float and travel through space. However, physics has proven this statement inaccurate and astronauts only weight about 10% less in space. According to Cutnell and Johnson this state of “weightlessness,” is not actually weightlessness and in turn should be referred to as apparent weightlessness [1]. In physics the concepts that best describes apparent weightlessness is uniform circular motion, gravity and applied force. According to Yale Scientific without gravity everything would cease to exist and because all matter would fly apart. Gravity is everywhere and it is the most important force in space and affects all matter. The gravitational pull from Earth is responsible for the moon’s orbit, and this gravitational force causes planets to orbit the sun. Because gravitational force relies on two masses which can explain why objects freely float in space. The smaller the mass the left gravitation force it feels. The further the object is from the sun the weaker its gravitation force.

An object’s weight is equal to gravity and the force acting upon the object. “True weight,” which is determined by the equation W=m*g by a weighing machine or balance, the true weight is equal to the force that is exerted by the Earth on it.

An example, When the stone is suspended by a spring balance the weight is by the normal contact force between the spring and the stone. If a stone was placed on a weighing scale, the force of gravity or its weight is acting downward is the force. The upward normal force from any supported surface is called an apparent weight, which depends on motion of the object or person. In addition, this further explains that a person on space would possess nearly the same weight as standing on the ground.

Another example of astronauts experiencing zero gravity is a person being inside an elevator, when the elevator is still the equation weight is equal to mass times gravity and equal to the force (W=mg=N), when the elevator moves down mass times acceleration is equal to mass times gravity minus the force (ma=mg-N), and when the elevator moves in an up direction, mass times acceleration is equal to force minus mass times gravity (ma=N-mg), the weight remains the same. When the elevator is falling freely the weight is zero because mass times gravity is equal to mass times gravity minus the force (mg=mg-N).

Therefore the apparent weight depends on motion, during free fall the person and weighing machine fall with the same acceleration. Astronauts remain in free fall, the astronauts does not exert any force and experiences weightlessness. As aforementioned, weightless is experienced because the astronaut and the weighing machine are free-falling at the same acceleration, and movement contributes a huge portion in weightlessness.

In result, in regards to astronauts in space, their weight does not change. Due to free-fall the astronaut has no force to support its body because the astronaut is accelerating down at the acceleration of gravity. In other words, you still have weight in gravity even though at certain times you cannot feel it. Many believe that the force allows you to stand on the ground is your own force. However, it is the force from the ground or anything that lies under you that pushes you back up. If there is nothing beneath you then you are in continuous free fall. For example different accelerations of apparent weight can occur when you on a rollercoaster or plane because at certain points of time you are traveling upward and other times downward.

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