When
we mean weight in general, we are implying the amount of human body material
that we possess in us. That is 50 Kg etc.. But in physics weight
means the force of gravity that the earth is exerting on a body, that possesses
mass.
Any
body or object that occupies space has a mass (amount of matter). This object
is attracted towards the earth's center by a force called gravitational
force. That is why an apple thrown high in to the sky returns back to the
surface of earth. If possible it will travel to the center of Earth deep
inside.
This
force of attraction by the gravitational principles is called the weight.
It is equal to mass multiplied with g = 9.81m/sec. on the surface of
earth. A person with a mass 50 Kg is actually 490.5 Newtons heavy. This force is felt by us at the
bottom of our feet.
When
a Lift (elevator) goes up, we feel heavier or lighter during brief
moments. This is because the Lift exerts some force in the upward
direction or downward direction. That adds to or reduces the effect of
gravity. More pronounced is the weightlessness or heaviness experienced
when one goes on a giant wheel, roller coaster, water slide ...
So
weight is a force. All the persons inside a satellite in distant space
feel weightless. All the objects, floor, ceiling, tables, astronauts are moving
at the same speed in the same direction in space around the Earth. So one
person does not feel heavy under the feet on the floor. Truely speaking they
have weight, but they do not feel it.
Weight is a force that depends on the mass (50 gms or 50 kgs or pounds) and the attraction of the planet on which we reside. If we go on to the Moon, the attraction we experience from the moon is only 1/6th of that on Earth. So we fell very light and our weight becomes 1/6th only. A high jumper may be able to jump over a bar placed at 6 times higher than on earth, if he gets the same lift he does on earth by pushing the ground with his/her feet.
