In Physics, 'Work' is not just studying or sitting at a desk. Work is strictly defined as an action that happens when a force causes an object to move. The standard SI unit for measuring Work (and Energy) is the Joule (J).
The Joule is named after the famous English physicist James Prescott Joule.
Because Work and Energy are interchangeable concepts in physics, 1 Joule of Work requires exactly 1 Joule of Energy to perform.
In the CGS system, the unit of work is the Erg. (1 Joule = $10^7$ ergs).
To define the unit, we must look at the mathematical formula for Work: Work Done (W) = Force (F) $\times$ Displacement (S)
Using the formula above, if you apply a force of 1 Newton, and the object moves 1 meter, the work done is $1 \times 1 = 1$.
Definition: 1 Joule of work is said to be done when a force of exactly 1 Newton acting on a body moves it by a distance of exactly 1 meter in the direction of the applied force.
Imagine an apple sitting on a table. The apple weighs approximately 100 grams (which means gravity pulls it down with about 1 Newton of force). If you lift that apple straight up exactly 1 meter into the air, you have done approximately 1 Joule of physical work.
In physics, you have done Zero Joules of work. Because the displacement (movement) is zero, $W = F \times 0 = 0$. You wasted energy, but no mechanical work was done.
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