When a block in resting on a table (the table is on Earth) the table stops the block from going more down, from where does it get the energy to apply a force opposite to gravity?
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When the block is placed on the table the gravitational field initially performs work by pushing the table blade down until an equilibrium is reached in which all forces cancel. This work increases the potential, deformation, energy of the table. The origin of this potential energy is the electromagnetic attraction between nuclei and electrons in the atoms of the table. In the end the gravitational field performs work on the atoms in the table.
my2cts
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The block has two forces on it: the downward force of gravitational attraction due to the Earth and the upward force due to the block being in contact with the table.
These two forces are equal in magnitude and opposite in direction so the net force on the block is zero.
Work tranfers energy from one place to another or transforms one form of energy into another form of energy.
Work done is equal to the force times the distance moved along the direction of the force.
If the force does not move then no work is done so there is no transfer of energy from one place to another and there is also no conversion of one form of energy into another.
Farcher
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