The weight W (measured in Newton) of an object of mass m (measured in kilograms) is the force of gravity on it and given by
W = mg
When you sit on a chair, you can feel your weight because the chair exerts a normal reaction force on you. However, when you jump off a table you are in free fall, and there is no reaction force on you and you feel weightless.
The ‘weight’ that you feel is called your apparent weight. It is measured by the normal reaction force N. When you are at rest on a chair, your apparent weight is the same as your weight. When you are in free fall, your apparent weight is zero.
An astronaut of mass m kg in a space shuttle experiences an apparent weight which is different from the actual weight at takeoff.
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