Fizyka dla każdego

   What does it mean "to do a work"?    

For a school student it means to solve urgently the exercise that the teacher gave a week ago and the lesson is tomorrow morning. 

For a clerk it means to stay quietly and to resist from 8 am to 3 pm (say, in Poland),

For a worker harvesting the grain with a scythe it means the fatigue and the sweat.

None of these jobs is the work for the physicists. Even pushing a heavy trolley is not a work in physics.

Look for these two films from Himalaya*. The yaks are carrying a really heavy luggage. But strangely, they do not perform any work.

Why? Because they move these loads in horizontal. 

Conversely, the poor “trägers” (as we call them in German and in Polish) do a great work. They bring commodities up to the shelter.

In physics, the work is done if the objects are moved up, and no work is done, when the objects are carried) in horizontal. As we can see in the picture below.

Moving objects in horizontal in not a work in physics. To do a work in physics means to move objects up, like this crane.

Obviously, the physics and the real fatigue is not the same.  

(C)  Klaudia Gackowska, Grzegorz Karwasz, Kasia Wyborska

*Film: courtesy prof. Irek Grabowski 

Drawings: dr Krzysztof Rochowicz, from "Torun tex-book for physics. Mechanics" by G, Karwasz, M. Sadowska, K. Rochowicz, Sci, Ed. University Nicolaus Copernicus, Torun, 2010.