Originally Posted by **angelulloa87** is their any machine that can reduce the weight of something, dont know if its the right question? |

Yes, there is such a machine - it's called a rocket ship. Let me explain:

An object's weight is equal to the force of gravity acting upon it, and the general equation for this force is:

F = GMm/R^2

Here G is the gravitational constant, 'M' is the mass of the earth, 'm' is the mass of the object under consideration and R is the distance from the center of the Earth to the object. For object's at or near the surface of the earth the value of GM/r^2 is typically shortened to 'g,' which yields:

F = mg

The value of g is about 9.8 m/s^2.

So, to reduce an object's weight you can:

1. Reduce the object's mass. Not practical, other than through chemical or nuclear reactions, but I doubt that's something you want to consider.

2. Increase the value of 'R,' which means you move away from the Earth. If you place the object in a rocket and launch it into space its weight (i.e. gravitational attraction to Earth) is reduced.

3. Decrease the value of M/R^2. If you place the object on a different planet that has smaller value of M/R^2 the gravitational force is reduced. For example objects placed on the surface of the moon are said to weigh about 1/6 what they do on earth.

Hence the machine you use to reduce weight is a rocket ship, so you can put the object into space or on another planet.

Another thing to consider is that if you remain near the Earth's surface an object's weight is pretty much constant, but the net force required to suspend or support it (as measured by the scale in your diagram) can be reduced using dynamic means. For example - if you place the object in an elevator and accelerate the elevator downward at rate 'a' the force of the object on the scale is reduced by the amount of acceleration:

F= m(g-a)

If you make a=g, then F becomes zero. This is precisely what happend for an object in earth orbit - its rate of downward acceleration as it orbits is exactly equal to the acceleration due to gravity, and we refer to the object as being "weightless." Strictly speaking the object's weight hasn't changed at all, but the downward force as measured by the scale has - hence the scale is no longer an accurate measure of the weght.

MBW's earlier reply about the dynamic motion of the spring is along these same lines - as the spring/mass system oscillates the net force on the object changes. But once the spring comes to rest (no more dynamic movement) the weight of the object as measured by the scale settles to F=mg.