Weight is the force with which the earth attracts an object towards it. Weightlessness is the term used to describe the sensation of complete or almost complete dearth of weight. It can also be defined as the absence of gravity.
It is a condition of free fall, in which the effect of gravity is canceled by the centrifugal force growing from an orbital flight, thus there is no force of gravity acting on the objects. It can be accurately described as the condition in which the body does not feel its weight at all.
Example, When an apple falls from a tree, it won’t feel its weight. This condition which is experienced by anybody during a free fall is called weightlessness.
An individual feels weightless when no external objects are touching its body. This happens when all forces which may come in contact with the body are removed. These sensations are common in the state of free fall.
During the fall, the only primary force which acts on the body/object is gravity. This is why an individual would feel weightless during a free fall. However, weightlessness is only a sensation and should not be altered with reality pertaining to an individual who has lost weight. The concept of weightlessness has much to do with the presence and absence of contact forces rather than with weight.
Astronauts orbiting in space get the feeling of weightlessness as there is no external contact force in space when it comes to pushing or pulling upon their bodies. Gravity is the only force acting upon their body. Gravity being action at a distance force can’t be felt and therefore won’t provide any sensation of weight. That is why astronauts feel weightless in space.
Crew members of spacecraft are often subjected to the problems of weightlessness. It came into the limelight from the U.S. and early Soviet manned missions that there is a decrease in heart and respiration rates along with gradual loss of bone calcium and weight during short flights. These are temporary and a reversal of these effects occurs as soon as one returns back to earth.
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